What is an alkali?
Alkali
In chemistry, an alkali (; from Arabic: "al-qaly" "ashes of the saltwort") is a basic, ionic salt of an alkali metal or alkaline earth metal chemical element. An alkali also can be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The adjective alkaline is commonly, and alkalescent less often, used in English as a synonym for basic, especially for bases soluble in water. This broad use of the term is likely to have come about because alkalis were the first bases known to obey the Arrhenius definition of a base, and they are still among the most common bases.
Alkyne
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and no other functional groups form a homologous series with the general chemical formula . Alkynes are traditionally known as acetylenes, although the name "acetylene" also refers specifically to CH, known formally as ethyne using IUPAC nomenclature. Like other hydrocarbons, alkynes are generally hydrophobic but tend to be more reactive.
Alkali soil
Calcium Chloride is also used to reclaim alkali soils. CaCl converts NaCO into NaCl precipitating CaCO. NaCl is drained off by leaching water. Spent acid (HCl, HSO, etc.) can also be used to reduce the excess NaCO in the soil/water.
Where urea is made available cheaply to farmers, it is also used to reduce the soil alkalinity / salinity primarily. The NH (Ammonium) present in urea which is a weak cation releases the strong cation Na from the soil structure into water. Thus alkali soils absorb / consume more urea compared to other soils.
Alkali metal
Lithium and sodium react with carbon to form acetylides, LiC and NaC, which can also be obtained by reaction of the metal with acetylene. Potassium, rubidium, and caesium react with graphite; their atoms are intercalated between the hexagonal graphite layers, forming graphite intercalation compounds of formulae MC (dark grey, almost black), MC (dark grey, almost black), MC (blue), MC (steel blue), and MC (bronze) (M = K, Rb, or Cs). These compounds are over 200 times more electrically conductive than pure graphite, suggesting that the valence electron of the alkali metal is transferred to the graphite layers (e.g. ). Upon heating of KC, the elimination of potassium atoms results in the conversion in sequence to KC, KC, KC and finally KC. KC is a very strong reducing agent and is pyrophoric and explodes on contact with water. While the larger alkali metals (K, Rb, and Cs) initially form MC, the smaller ones initially form MC, and indeed they require reaction of the metals with graphite at high temperatures around 500 °C to form. Apart from this, the alkali metals are such strong reducing agents that they can even reduce buckminsterfullerene to produce solid fullerides MC; sodium, potassium, rubidium, and caesium can form fullerides where "n" = 2, 3, 4, or 6, and rubidium and caesium additionally can achieve "n" = 1.
Alkaloid
Alkaloids are produced by a large variety of organisms including bacteria, fungi, plants, and animals. They can be purified from crude extracts of these organisms by acid-base extraction. Alkaloids have a wide range of pharmacological activities including antimalarial ("e.g." quinine), antiasthma ("e.g." ephedrine), anticancer ("e.g." homoharringtonine), cholinomimetic ("e.g." galantamine), vasodilatory ("e.g." vincamine), antiarrhythmic ("e.g." quinidine), analgesic ("e.g." morphine), antibacterial ("e.g." chelerythrine), and antihyperglycemic activities ("e.g." piperine). Many have found use in traditional or modern medicine, or as starting points for drug discovery. Other alkaloids possess psychotropic ("e.g." psilocin) and stimulant activities ("e.g." cocaine, caffeine, nicotine, theobromine), and have been used in entheogenic rituals or as recreational drugs. Alkaloids can be toxic too ("e.g." atropine, tubocurarine). Although alkaloids act on a diversity of metabolic systems in humans and other animals, they almost uniformly evoke a bitter taste.
Halomonas alkaliphila
Halomonas alkaliphila is a Gram-negative halophilic Proteobacteria. Its specific epithet stems from the Arabic word "alkali" (al-qaliy), the ashes of saltwort and the Latin adjective "philus" -a -um, meaning "friend" or "loving": loving alkaline media.
Alkali hydroxide
The alkali metal hydroxides are the strongest of all bases.The order of basicity increases down the group, i.e., LiOH is the least basic and CsOH, the most basic hydroxide. It is due to the property of bases to donate ion and due to small size and high lattice enthalpy of Li, it donates less and large size and low lattice enthalpy of Cs, Cesium hydroxide donates more ions than any other hydroxide. All the alkali metal hydroxides are white crystalline solids and dissolve freely in water with evolution of much heat.
Acid–base reaction
This causes the protonation of water, or the creation of the hydronium (HO) ion. Thus, in modern times, the symbol H is interpreted as a shorthand for HO, because it is now known that a bare proton does not exist as a free species in aqueous solution.
The Arrhenius definitions of acidity and alkalinity are restricted to aqueous solutions, and refer to the concentration of the solvent ions. Under this definition, pure HSO and HCl dissolved in toluene are not acidic, and molten NaOH and solutions of calcium amide in liquid ammonia are not alkaline. This led to the development of the Bronsted-Lowry theory and subsequent Lewis theory to account for these non-aqueous exceptions.
Alkali metal
When the alkali metals react with the heavier elements in the carbon group (silicon, germanium, tin, and lead), ionic substances with cage-like structures are formed, such as the silicides MSi (M = K, Rb, or Cs), which contains M and tetrahedral ions. The chemistry of alkali metal germanides, involving the germanide ion Ge and other cluster (Zintl) ions such as , , , and [(Ge)], is largely analogous to that of the corresponding silicides. Alkali metal stannides are mostly ionic, sometimes with the stannide ion (Sn), and sometimes with more complex Zintl ions such as , which appears in tetrapotassium nonastannide (KSn). The monatomic plumbide ion (Pb) is unknown, and indeed its formation is predicted to be energetically unfavourable; alkali metal plumbides have complex Zintl ions, such as . These alkali metal germanides, stannides, and plumbides may be produced by reducing germanium, tin, and lead with sodium metal in liquid ammonia.
Naphthalene
With alkali metals, naphthalene forms the dark blue-green radical anion salts such as sodium naphthalenide, NaCH. The naphthalenide salts are strong reducing agents.
Alkaliphile
Microbial growth in alkaline conditions presents several complications to normal biochemical activity and reproduction, as high pH is detrimental to normal cellular processes. For example, alkalinity can lead to denaturation of DNA, instability of the plasma membrane and inactivation of cytosolic enzymes, as well as other unfavorable physiological changes. Thus, to adequately circumvent these obstacles, alkaliphiles must either possess specific cellular machinery that works best in the alkaline range, or they must have methods of acidifying the cytosol in relation to the extracellular environment. To determine which of the above possibilities an alkaliphile uses, experimentation has demonstrated that alkaliphilic enzymes possess relatively normal pH optimums. The determination that these enzymes function most efficiently near physiologically neutral pH ranges (about 7.5–8.5) was one of the primary steps in elucidating how alkaliphiles survive intensely basic environments. Since the cytosolic pH must remain nearly neutral, alkaliphiles must have one or more mechanisms of acidifying the cytosol when in the presence of a highly alkaline environment.
Alkaline earth metal
The alkaline earth metals are named after their oxides, the "alkaline earths", whose old-fashioned names were beryllia, magnesia, lime, strontia, and baryta. These oxides are basic (alkaline) when combined with water. "Earth" is an old term applied by early chemists to nonmetallic substances that are insoluble in water and resistant to heating—properties shared by these oxides. The realization that these earths were not elements but compounds is attributed to the chemist Antoine Lavoisier. In his "Traité Élémentaire de Chimie" ("Elements of Chemistry") of 1789 he called them salt-forming earth elements. Later, he suggested that the alkaline earths might be metal oxides, but admitted that this was mere conjecture. In 1808, acting on Lavoisier's idea, Humphry Davy became the first to obtain samples of the metals by electrolysis of their molten earths, thus supporting Lavoisier's hypothesis and causing the group to be named the "alkaline earth metals".
Alkali metal
The coinage metals were traditionally regarded as a subdivision of the alkali metal group, due to them sharing the characteristic s electron configuration of the alkali metals (group 1: ps; group 11: ds). However, the similarities are largely confined to the stoichiometries of the +1 compounds of both groups, and not their chemical properties. This stems from the filled d subshell providing a much weaker shielding effect on the outermost s electron than the filled p subshell, so that the coinage metals have much higher first ionisation energies and smaller ionic radii than do the corresponding alkali metals. Furthermore, they have higher melting points, hardnesses, and densities, and lower reactivities and solubilities in liquid ammonia, as well as having more covalent character in their compounds. Finally, the alkali metals are at the top of the electrochemical series, whereas the coinage metals are almost at the very bottom. The coinage metals' filled d shell is much more easily disrupted than the alkali metals' filled p shell, so that the second and third ionisation energies are lower, enabling higher oxidation states than +1 and a richer coordination chemistry, thus giving the group 11 metals clear transition metal character. Particularly noteworthy is gold forming ionic compounds with rubidium and caesium, in which it forms the auride ion (Au) which also occurs in solvated form in liquid ammonia solution: here gold behaves as a pseudohalogen because its 5d6s configuration has one electron less than the quasi-closed shell 5d6s configuration of mercury.
Alkali manufacture
Alkali manufacture is the process by which an alkali is made. Typical alkalis, produced commercially, include sodium hydroxide, sodium carbonate, potassium hydroxide and potassium carbonate.
Amine alkylation
Industrially, most alkylations are typically conducted using alcohols, not alkyl halides. Alcohols are less expensive than alkyl halides and their alkylation does not produce salts, the disposal of which can be problematic. Key to the alkylation of alcohols is the use of catalysts that render the hydroxyl group a good leaving group. The largest scale "N"-alkylation is the production of the methylamines from ammonia and methanol, resulting in approximately 500,000 tons/y of methylamine, dimethylamine, and trimethylamine. The reaction is poorly selective, requiring separation of the three products. Many other industrially significant alkyl amines are produced, again on a large scale, from the alcohols. Epoxides are another class of halide-free "N"-alkylating agents, useful in the production of ethanolamines.
Alkali metal
All the alkali metals react vigorously with oxygen at standard conditions. They form various types of oxides, such as simple oxides (containing the O ion), peroxides (containing the ion, where there is a single bond between the two oxygen atoms), superoxides (containing the ion), and many others. Lithium burns in air to form lithium oxide, but sodium reacts with oxygen to form a mixture of sodium oxide and sodium peroxide. Potassium forms a mixture of potassium peroxide and potassium superoxide, while rubidium and caesium form the superoxide exclusively. Their reactivity increases going down the group: while lithium, sodium and potassium merely burn in air, rubidium and caesium are pyrophoric (spontaneously catch fire in air).
Alkali metal nitrate
Alkali metal nitrates are chemical compounds consisting of an alkali metal (lithium, sodium, potassium, rubidium and caesium) and the nitrate ion. Only two are of major commercial value, the sodium and potassium salts. They are white, water-soluble salts with relatively similar melting points.
The main uses of alkali metal nitrates are in fertilizers in the case of the sodium and potassium derivatives. They are also commonly used in explosives and pyrotechnic compositions; they are strong oxidizers. Other uses are for coloring in fireworks: caesium nitrate produces an indigo color, potassium nitrate and rubidium nitrate produce violet colors, lithium nitrate produces a red color, and sodium nitrate produces a yellow color.
Alkenal
An alkenal is a class of chemical compound that includes the aldehyde and alkene functional groups.
Sodium aluminium hydride
Sodium aluminium hydride or sodium alanate is an inorganic compound with the chemical formula NaAlH. It is a white pyrophoric solid that dissolves in tetrahydrofuran (THF), but not in diethyl ether or hydrocarbons. It has been evaluated as an agent for the reversible storage of hydrogen and it is used as a reagent for the chemical synthesis of organic compounds. Similar to lithium aluminium hydride, it is a salt consisting of separated sodium cations and tetrahedral AlH anions.
Alkali metal
Alkali metal cations do not usually form coordination complexes with simple Lewis bases due to their low charge of just +1 and their relatively large size; thus the Li ion forms most complexes and the heavier alkali metal ions form less and less (though exceptions occur for weak complexes). Lithium in particular has a very rich coordination chemistry in which it exhibits coordination numbers from 1 to 12, although octahedral hexacoordination is its preferred mode. In aqueous solution, the alkali metal ions exist as octahedral hexahydrate complexes ([M(HO))]), with the exception of the lithium ion, which due to its small size forms tetrahedral tetrahydrate complexes ([Li(HO))]); the alkali metals form these complexes because their ions are attracted by electrostatic forces of attraction to the polar water molecules. Because of this, anhydrous salts containing alkali metal cations are often used as desiccants. Alkali metals also readily form complexes with crown ethers (e.g. 12-crown-4 for Li, 15-crown-5 for Na, 18-crown-6 for K, and 21-crown-7 for Rb) and cryptands due to electrostatic attraction.
Alkali hydroxide
All alkali hydroxides are very corrosive, being strongly alkaline.
Alkene
Alkenes are ligands in transition metal alkene complexes. The two carbon centres bond to the metal using the C–C pi- and pi*-orbitals. Mono- and diolefins are often used as ligands in stable complexes. Cyclooctadiene and norbornadiene are popular chelating agents, and even ethylene itself is sometimes used as a ligand, for example, in Zeise's salt. In addition, metal–alkene complexes are intermediates in many metal-catalyzed reactions including hydrogenation, hydroformylation, and polymerization.
Alkane
Alkanes do not conduct electricity in any way, nor are they substantially polarized by an electric field. For this reason, they do not form hydrogen bonds and are insoluble in polar solvents such as water. Since the hydrogen bonds between individual water molecules are aligned away from an alkane molecule, the coexistence of an alkane and water leads to an increase in molecular order (a reduction in entropy). As there is no significant bonding between water molecules and alkane molecules, the second law of thermodynamics suggests that this reduction in entropy should be minimized by minimizing the contact between alkane and water: Alkanes are said to be hydrophobic in that they repel water.
Alkaloid
Most alkaloids are weak bases, but some, such as theobromine and theophylline, are amphoteric. Many alkaloids dissolve poorly in water but readily dissolve in organic solvents, such as diethyl ether, chloroform or 1,2-dichloroethane. Caffeine, cocaine, codeine and nicotine are slightly soluble in water (with a solubility of ≥1g/L), whereas others, including morphine and yohimbine are very slightly water-soluble (0.1–1 g/L). Alkaloids and acids form salts of various strengths. These salts are usually freely soluble in water and ethanol and poorly soluble in most organic solvents. Exceptions include scopolamine hydrobromide, which is soluble in organic solvents, and the water-soluble quinine sulfate.
Alkaline diet
Nutrition scientists began to refine this hypothesis in the early 20th century, emphasizing the role of negatively charged particles (anions) and positively charged particles (cations) in food. Diets high in chloride, phosphate and sulfate (all of which are anions) were presumed to be acid forming, while diets high in potassium, calcium and magnesium (all of which are cations) were presumed to be alkaline forming. Other investigations showed specific foods, such as cranberries, prunes and plums had unusual effects on urine pH. While these foods provided an alkaline ash in the laboratory, they contain a weak organic acid, hippuric acid, which caused the urine to become more acidic instead.
ALPI
Alkaline phosphatase, intestinal also known as ALPI is a type of alkaline phosphatase that in humans is encoded by the "ALPI" gene.
Alkali metal
The ammonium ion () has very similar properties to the heavier alkali metals, acting as an alkali metal intermediate between potassium and rubidium, and is often considered a close relative. For example, most alkali metal salts are soluble in water, a property which ammonium salts share. Ammonium is expected to behave stably as a metal ( ions in a sea of delocalised electrons) at very high pressures (though less than the typical pressure where transitions from insulating to metallic behaviour occur around, 100 GPa), and could possibly occur inside the ice giants Uranus and Neptune, which may have significant impacts on their interior magnetic fields. It has been estimated that the transition from a mixture of ammonia and dihydrogen molecules to metallic ammonium may occur at pressures just below 25 GPa. Under standard conditions, ammonium can form a metallic amalgam with mercury.
Period 2 element
Lithium (Li) is an alkali metal with atomic number 3, occurring naturally in two isotopes: Li and Li. The two make up all natural occurrence of lithium on Earth, although further isotopes have been synthesized. In ionic compounds, lithium loses an electron to become positively charged, forming the cation Li. Lithium is the first alkali metal in the periodic table, and the first metal of any kind in the periodic table. At standard temperature and pressure, lithium is a soft, silver-white, highly reactive metal. With a density of 0.564 g·cm, lithium is the lightest metal and the least dense solid element.
Alkaloid
Biological precursors of most alkaloids are amino acids, such as ornithine, lysine, phenylalanine, tyrosine, tryptophan, histidine, aspartic acid, and anthranilic acid. Nicotinic acid can be synthesized from tryptophan or aspartic acid. Ways of alkaloid biosynthesis are too numerous and cannot be easily classified. However, there are a few typical reactions involved in the biosynthesis of various classes of alkaloids, including synthesis of Schiff bases and Mannich reaction.
Cleaning agent
Alkaline cleaning agents contain strong bases like sodium hydroxide or potassium hydroxide. Bleach (pH 12) and ammonia (pH 11) are common alkaline cleaning agents. Often, dispersants, to prevent redeposition of dissolved dirt, and chelants, to attack rust, are added to the alkaline agent.
Alkaline phosphatase
Alkaline phosphatase (ALP, ALKP, ALPase, Alk Phos) () or basic phosphatase is a homodimeric protein enzyme of 86 kilodaltons. Each monomer contains five cysteine residues, two zinc atoms, and one magnesium atom crucial to its catalytic function, and it is optimally active at alkaline pH environments. ALP has the physiological role of dephosphorylating compounds. The enzyme is found across a multitude of organisms, prokaryotes and eukaryotes alike, with the same general function but in different structural forms suitable to the environment they function in. Alkaline phosphatase is found in the periplasmic space of E. coli bacteria. This enzyme is heat stable and has its maximum activity at high pH. In humans, it is found in many forms depending on its origin within the body – it plays an integral role in metabolism within the liver and development within the skeleton. Due to its widespread prevalence in these areas, its concentration in the bloodstream is used by diagnosticians as a biomarker in helping determine diagnoses such as hepatitis or osteomalacia.
Alkyl
In organic chemistry, an alkyl substituent is an alkane missing one hydrogen.
The term alkyl is intentionally unspecific to include many possible substitutions. 
An acyclic alkyl has the general formula CH. A cycloalkyl is derived from a cycloalkane by removal of a hydrogen atom from a ring and has the general formula CH.
Typically an alkyl is a part of a larger molecule. In structural formula, the symbol R is used to designate a generic (unspecified) alkyl group. The smallest alkyl group is methyl, with the formula CH−. Although the name 'alkyl' is strictly given to straight chain alkyls only. For branched chain alkyls, terms like "iso", "neo" are often used along with the word "alkyl".
The word root "alkyl" is encountered in several contexts. Alkylation is an important operation in refineries, for example in the production of high-octane gasoline. Alkylating antineoplastic agents refer to a class of compounds that are used to treat cancer. In such case, the term alkyl is used loosely. For example, nitrogen mustards are well-known alkylating agents, but they are more complex than a mere hydrocarbon. In chemistry, alkyl refers to a group, a substituent, that is attached to other molecular fragments. For example, alkyl lithium reagents have the empirical formula Li(alkyl), where alkyl = methyl, ethyl, etc. A "dialkyl" ether is an ether with two alkyl groups, e.g., diethyl ether (O(CH)). Alkyl also refers to an active ingredient in green algae preventatives used in swimming pools.
Alkali metal
Pure alkali metals are dangerously reactive with air and water and must be kept away from heat, fire, oxidising agents, acids, most organic compounds, halocarbons, plastics, and moisture. They also react with carbon dioxide and carbon tetrachloride, so that normal fire extinguishers are counterproductive when used on alkali metal fires. Some Class D dry powder extinguishers designed for metal fires are effective, depriving the fire of oxygen and cooling the alkali metal.
Alkali metal
Around 1865 John Newlands produced a series of papers where he listed the elements in order of increasing atomic weight and similar physical and chemical properties that recurred at intervals of eight; he likened such periodicity to the octaves of music, where notes an octave apart have similar musical functions. His version put all the alkali metals then known (lithium to caesium), as well as copper, silver, and thallium (which show the +1 oxidation state characteristic of the alkali metals), together into a group. His table placed hydrogen with the halogens.
After 1869, Dmitri Mendeleev proposed his periodic table placing lithium at the top of a group with sodium, potassium, rubidium, caesium, and thallium. Two years later, Mendeleev revised his table, placing hydrogen in group 1 above lithium, and also moving thallium to the boron group. In this 1871 version, copper, silver, and gold were placed twice, once as part of group IB, and once as part of a "group VIII" encompassing today's groups 8 to 11. After the introduction of the 18-column table, the group IB elements were moved to their current position in the d-block, while alkali metals were left in "group IA". Later the group's name was changed to "group 1" in 1988. The trivial name "alkali metals" comes from the fact that the hydroxides of the group 1 elements are all strong alkalis when dissolved in water.
Alkali metal
The hydroxides themselves are the most basic hydroxides known, reacting with acids to give salts and with alcohols to give oligomeric alkoxides. They easily react with carbon dioxide to form carbonates or bicarbonates, or with hydrogen sulfide to form sulfides or bisulfides, and may be used to separate thiols from petroleum. They react with amphoteric oxides: for example, the oxides of aluminium, zinc, tin, and lead react with the alkali metal hydroxides to give aluminates, zincates, stannates, and plumbates. Silicon dioxide is acidic, and thus the alkali metal hydroxides can also attack silicate glass.
Alkali metal
In aqueous solution, the alkali metal ions form aqua ions of the formula [M(HO)], where "n" is the solvation number. Their coordination numbers and shapes agree well with those expected from their ionic radii. In aqueous solution the water molecules directly attached to the metal ion are said to belong to the first coordination sphere, also known as the first, or primary, solvation shell. The bond between a water molecule and the metal ion is a dative covalent bond, with the oxygen atom donating both electrons to the bond. Each coordinated water molecule may be attached by hydrogen bonds to other water molecules. The latter are said to reside in the second coordination sphere. However, for the alkali metal cations, the second coordination sphere is not well-defined as the +1 charge on the cation is not high enough to polarise the water molecules in the primary solvation shell enough for them to form strong hydrogen bonds with those in the second coordination sphere, producing a more stable entity. The solvation number for Li has been experimentally determined to be 4, forming the tetrahedral [Li(HO)]: while solvation numbers of 3 to 6 have been found for lithium aqua ions, solvation numbers less than 4 may be the result of the formation of contact ion pairs, and the higher solvation numbers may be interpreted in terms of water molecules that approach [Li(HO)] through a face of the tetrahedron, though molecular dynamic simulations may indicate the existence of an octahedral hexaaqua ion. There are also probably six water molecules in the primary solvation sphere of the sodium ion, forming the octahedral [Na(HO)] ion. While it was previously thought that the heavier alkali metals also formed octahedral hexaaqua ions, it has since been found that potassium and rubidium probably form the [K(HO)] and [Rb(HO)] ions, which have the square antiprismatic structure, and that caesium forms the 12-coordinate [Cs(HO)] ion.
The chemistry of lithium shows several differences from that of the rest of the group as the small Li cation polarises anions and gives its compounds a more covalent character. Lithium and magnesium have a diagonal relationship due to their similar atomic radii, so that they show some similarities. For example, lithium forms a stable nitride, a property common among all the alkaline earth metals (magnesium's group) but unique among the alkali metals. In addition, among their respective groups, only lithium and magnesium form organometallic compounds with significant covalent character (e.g. LiMe and MgMe).
Alkali metal
All the alkali metals have odd atomic numbers; hence, their isotopes must be either odd–odd (both proton and neutron number are odd) or odd–even (proton number is odd, but neutron number is even). Odd–odd nuclei have even mass numbers, whereas odd–even nuclei have odd mass numbers. Odd–odd primordial nuclides are rare because most odd–odd nuclei are highly unstable with respect to beta decay, because the decay products are even–even, and are therefore more strongly bound, due to nuclear pairing effects.
Alkali metal oxide
The alkali metals react with oxygen to form several different compounds: suboxides, oxides, peroxides, superoxides, and ozonides. They all react violently with water.
Alkalinity
Alkalinity or A measures the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate. The alkalinity is equal to the stoichiometric sum of the bases in solution. In the natural environment carbonate alkalinity tends to make up most of the total alkalinity due to the common occurrence and dissolution of carbonate rocks and presence of carbon dioxide in the atmosphere. Other common natural components that can contribute to alkalinity include borate, hydroxide, phosphate, silicate, dissolved ammonia, the conjugate bases of some organic acids, and sulfate. Solutions produced in a laboratory may contain a virtually limitless number of bases that contribute to alkalinity. Alkalinity is usually given in the unit mEq/L (milliequivalent per liter). Commercially, as in the swimming pool industry, alkalinity might also be given in parts per million of equivalent calcium carbonate (ppm CaCO).
Alkali Lake (Oregon)
Alkali Lake is a geographic sink in Lake County, Oregon, United States. It is in the Alkali Subbasin of the Summer Lake Basin watershed in southeastern Oregon, located 26 miles east of Christmas Valley, Oregon, northeast of Lake Abert, to the immediate west of Abert Rim and Highway 395.
Alkene
Alkenes are relatively stable compounds, but are more reactive than alkanes, either because of the reactivity of the carbon–carbon pi-bond or the presence of allylic CH centers. Most reactions of alkenes involve additions to this pi bond, forming new single bonds. Alkenes serve as a feedstock for the petrochemical industry because they can participate in a wide variety of reactions, prominently polymerization and alkylation.
Alkali salt
Another definition of a basic salt would be a salt that contains amounts of both hydroxide and other anions. White lead is an example. It is basic lead carbonate, or lead carbonate hydroxide.
Alkali basalt
Alkali basalt or alkali olivine basalt is a fine-grained, dark-coloured, volcanic rock characterized by phenocrysts of olivine, titanium-rich augite, plagioclase feldspar and iron oxides. For similar SiO concentrations, alkali basalts have a higher content of the alkalis, NaO and KO, than other basalt types such as tholeiites. They are also characterized by the development of modal nepheline in their groundmass (visible at highest magnification on a petrographic microscope) and normative nepheline in their CIPW norms. Alkali basalts are typically found on updomed and rifted continental crust, and on oceanic islands such as Hawaii, Madeira and Ascension Island.
Alkali metal
All the alkali metals react vigorously or explosively with cold water, producing an aqueous solution of a strongly basic alkali metal hydroxide and releasing hydrogen gas. This reaction becomes more vigorous going down the group: lithium reacts steadily with effervescence, but sodium and potassium can ignite and rubidium and caesium sink in water and generate hydrogen gas so rapidly that shock waves form in the water that may shatter glass containers. When an alkali metal is dropped into water, it produces an explosion, of which there are two separate stages. The metal reacts with the water first, breaking the hydrogen bonds in the water and producing hydrogen gas; this takes place faster for the more reactive heavier alkali metals. Second, the heat generated by the first part of the reaction often ignites the hydrogen gas, causing it to burn explosively into the surrounding air. This secondary hydrogen gas explosion produces the visible flame above the bowl of water, lake or other body of water, not the initial reaction of the metal with water (which tends to happen mostly under water). The alkali metal hydroxides are the most basic known hydroxides.
Alkali metal
The physical and chemical properties of the alkali metals can be readily explained by their having an ns valence electron configuration, which results in weak metallic bonding. Hence, all the alkali metals are soft and have low densities, melting and boiling points, as well as heats of sublimation, vaporisation, and dissociation. They all crystallise in the body-centered cubic crystal structure, and have distinctive flame colours because their outer s electron is very easily excited. The ns configuration also results in the alkali metals having very large atomic and ionic radii, as well as very high thermal and electrical conductivity. Their chemistry is dominated by the loss of their lone valence electron in the outermost s-orbital to form the +1 oxidation state, due to the ease of ionising this electron and the very high second ionisation energy. Most of the chemistry has been observed only for the first five members of the group. The chemistry of francium is not well established due to its extreme radioactivity; thus, the presentation of its properties here is limited. What little is known about francium shows that it is very close in behaviour to caesium, as expected. The physical properties of francium are even sketchier because the bulk element has never been observed; hence any data that may be found in the literature are certainly speculative extrapolations.
On a New Organic Base in the Coca Leaves
On a New Organic Base in the Coca Leaves is an 1860 dissertation written by Dr. Albert Niemann. Its title in German is "Über eine neue organische Base in den Cocablättern". The piece describes, in detail, how Niemann isolated cocaine, a crystalline alkaloid. It also earned Niemann his Ph.D. and is now in the British Library. He wrote of the alkaloid's "colourless transparent prisms" and said that, "Its solutions have an alkaline reaction, a bitter taste, promote the flow of saliva and leave a peculiar numbness, followed by a sense of cold when applied to the tongue." Niemann named the alkaloid "cocaine" — as with other alkaloids its name carried the "-ine" suffix.
Alkali
Alkalis are all Arrhenius bases, ones which form hydroxide ions (OH) when dissolved in water. Common properties of alkaline aqueous solutions include:
Salt (chemistry)
Salts can be classified in a variety of ways. Salts that produce hydroxide ions when dissolved in water are called alkali salts. Salts that produce acidic solutions are "acidic salts". "Neutral salts" are those salts that are neither acidic nor basic. Zwitterions contain an anionic and a cationic centres in the same molecule, but are not considered to be salts. Examples of zwitterions include amino acids, many metabolites, peptides, and proteins.
Potassium
Potassium is a chemical element with symbol K (from Neo-Latin "kalium") and atomic number 19. It was first isolated from potash, the ashes of plants, from which its name derives. In the periodic table, potassium is one of the alkali metals. All of the alkali metals have a single valence electron in the outer electron shell, which is easily removed to create an ion with a positive charge – a cation, which combines with anions to form salts. Potassium in nature occurs only in ionic salts. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and reacts vigorously with water, generating sufficient heat to ignite hydrogen emitted in the reaction, and burning with a lilac-colored flame. It is found dissolved in sea water (which is 0.04% potassium by weight), and is part of many minerals.
Alkali metal
All the alkali metals react readily with phosphorus and arsenic to form phosphides and arsenides with the formula MPn (where M represents an alkali metal and Pn represents a pnictogen – phosphorus, arsenic, antimony, or bismuth). This is due to the greater size of the P and As ions, so that less lattice energy needs to be released for the salts to form. These are not the only phosphides and arsenides of the alkali metals: for example, potassium has nine different known phosphides, with formulae KP, KP, KP, KP, KP, KP, KP, KP, and KP. While most metals form arsenides, only the alkali and alkaline earth metals form mostly ionic arsenides. The structure of NaAs is complex with unusually short Na–Na distances of 328–330 pm which are shorter than in sodium metal, and this indicates that even with these electropositive metals the bonding cannot be straightforwardly ionic. Other alkali metal arsenides not conforming to the formula MAs are known, such as LiAs, which has a metallic lustre and electrical conductivity indicating the presence of some metallic bonding. The antimonides are unstable and reactive as the Sb ion is a strong reducing agent; reaction of them with acids form the toxic and unstable gas stibine (SbH). Indeed, they have some metallic properties, and the alkali metal antimonides of stoichiometry MSb involve antimony atoms bonded in a spiral Zintl structure. Bismuthides are not even wholly ionic; they are intermetallic compounds containing partially metallic and partially ionic bonds.
Alkali metal
The alkali metals are among the most electropositive elements on the periodic table and thus tend to bond ionically to the most electronegative elements on the periodic table, the halogens (fluorine, chlorine, bromine, iodine, and astatine), forming salts known as the alkali metal halides. The reaction is very vigorous and can sometimes result in explosions. All twenty stable alkali metal halides are known; the unstable ones are not known, with the exception of sodium astatide, because of the great instability and rarity of astatine and francium. The most well-known of the twenty is certainly sodium chloride, otherwise known as common salt. All of the stable alkali metal halides have the formula MX where M is an alkali metal and X is a halogen. They are all white ionic crystalline solids that have high melting points. All the alkali metal halides are soluble in water except for lithium fluoride (LiF), which is insoluble in water due to its very high lattice enthalpy. The high lattice enthalpy of lithium fluoride is due to the small sizes of the Li and F ions, causing the electrostatic interactions between them to be strong: a similar effect occurs for magnesium fluoride, consistent with the diagonal relationship between lithium and magnesium.
Alkalinity
Alkalinity roughly refers to the amount of bases in a solution that can be converted to uncharged species by a strong acid. The cited author, James Drever, provides an equation expressed in terms of molar equivalents, which means the number of moles of each ion type multiplied by (the absolute value of) the charge of the ion. For example, 1 mole of HCO in solution represents 1 molar equivalent, while 1 mole of CO is 2 molar equivalents because twice as many H ions would be necessary to balance the charge. The total charge of a solution always equals zero.
Alkyl phosphate
Alkyl phosphates belong to a group of organic compounds called organophosphates. They are esters of phosphoric acid HPO and corresponding alcohol. For example, the formula of methyl phosphate is CH-HPO, dimethyl phosphate – (CH)HPO and trimethyl phosphate – (CH)PO. 
Alkyl phosphates are widely distributed in nature, and form the basis of most biological processes. For example, high energy metabolites such as ATP and PEP are alkyl phosphates, as are nucleic acids such as DNA and RNA. Alkyl phosphates are also important medicinally, for example the HIV drug AZT is inactive until it becomes an alkyl phosphate in vivo.
Alkyl
Usually, alkyl groups are attached to other atoms or groups of atoms. Free alkyls occur as neutral species, as anions, or as cations. The cations are called carbocations. The anions are called carbanions. The neutral alkyl free radicals have no special name. Such species are usually encountered only as transient intermediates, but some are quite stable and can be "put into a bottle". Typically alkyl cations are generated using super acids, alkyl anions are observed in the presence of strong bases, and alkyl radicals are generated by a photochemical reaction. Alkyls are commonly observed in mass spectrometry of organic compounds.
Alkali soil
Carbonic acid HCO is unstable and produces HO (water) and CO (carbon dioxide gas, escaping into the atmosphere). This explains the remaining alkalinity (or rather basicity) in the form of soluble sodium hydroxide and the high pH or low pOH.
Alkalibacterium
The generic name "Alkalibacterium" derives from: Latin "alkali" (ashes of saltwort) alkali; and "bacterium", a small rod, to give "a bacterium living under alkaline conditions".
Alkaloid
Most alkaloids contain oxygen in their molecular structure; those compounds are usually colorless crystals at ambient conditions. Oxygen-free alkaloids, such as nicotine or coniine, are typically volatile, colorless, oily liquids. Some alkaloids are colored, like berberine (yellow) and sanguinarine (orange).
Alkalosis
Alkalosis is the result of a process reducing hydrogen ion concentration of arterial blood plasma (alkalemia). In contrast to acidemia (serum pH 7.35 or lower), alkalemia occurs when the serum pH is higher than normal (7.45 or higher). Alkalosis is usually divided into the categories of respiratory alkalosis and metabolic alkalosis or a combined respiratory/metabolic alkalosis.
Alkali metal
The alkali metals are a group (column) in the periodic table consisting of the chemical elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). This group lies in the s-block of the periodic table of elements as all alkali metals have their outermost electron in an s-orbital: this shared electron configuration results in their having very similar characteristic properties. Indeed, the alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting well-characterised homologous behaviour.
Alkali metal
The alkali metals are all shiny, soft, highly reactive metals at standard temperature and pressure and readily lose their outermost electron to form cations with charge +1. They can all be cut easily with a knife due to their softness, exposing a shiny surface that tarnishes rapidly in air due to oxidation by atmospheric moisture and oxygen (and in the case of lithium, nitrogen). Because of their high reactivity, they must be stored under oil to prevent reaction with air, and are found naturally only in salts and never as the free elements. Caesium, the fifth alkali metal, is the most reactive of all the metals. In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, excluding hydrogen (H), which is nominally a group 1 element but not normally considered to be an alkali metal as it rarely exhibits behaviour comparable to that of the alkali metals. All the alkali metals react with water, with the heavier alkali metals reacting more vigorously than the lighter ones.
Alkane
An alkyl group, generally abbreviated with the symbol R, is a functional group that, like an alkane, consists solely of single-bonded carbon and hydrogen atoms connected acyclically—for example, a methyl or ethyl group.
Alkali salt
These salts are insoluble and are obtained through precipitation reactions.'Alkaline salts' are often the major component of alkaline dishwasher detergent powders.
Alkalide
Normally, alkalides are thermally labile due to the high reactivity of the alkalide anion, which is theoretically able to break most covalent bonds including the C–O bonds in a typical cryptand. The introduction of a special cryptand ligand containing amines instead of ether linkages has allowed the isolation of kalides and natrides that are stable at room temperature.
Chalcogenide
Alkali metal and alkaline earth monochalcogenides are salt-like, being colourless and often water-soluble. The sulfides tend to undergo hydrolysis to form derivatives containing bisulfide (SH) anions. The alkali metal chalcogenides often crystallize with the antifluorite structure and the alkaline earth salts in the sodium chloride motif.
Alkali (disambiguation)
Alkali may refer to:
Alkali Lakes (California)
The Alkali Lakes are a series of three large playas located in the Surprise Valley of northeastern California, United States. From north to south they are known as Upper, Middle and Lower Alkali Lake. Upper Alkali Lake is often known simply as Upper Lake, and Lower Alkali Lake as Lower Lake. Although mostly located in Modoc County, California, the eastern edges of Middle and Lower Lakes touch Washoe County, Nevada. The Warner Mountains are located to the west of the three lakes. The lake beds are typically flooded with shallow water in the winter but dry up during most summers.
Mohammad Al-Ali
- that alkrasi
Acidic oxide
Although it is difficult to classify these oxides as acids, the property is manifest in reactions with bases. For example, carbon dioxide reacts with alkali.
For this reason, alkali is kept in stoppered vessels to inhibit reaction with atmospheric carbon dioxide. In geochemistry complex silicates are often written as though they are the products of an acid-base reaction. For example, the chemical formula of the mineral olivine can be written either as (Mg,Fe)SiO or as (MgO,FeO)SiO. This mineral is said to be ultramafic, meaning that it has a very high nominal content of the bases magnesium oxide and iron oxide and hence, a low content of the acid silicon dioxide.Aluminium oxide (AlO) is an amphoteric oxide; it can act as a base or acid. For example with base different aluminate salts will be formed:
Alkali metal
Thallium is the heaviest stable element in group 13 of the periodic table. At the bottom of the periodic table, the inert pair effect is quite strong, because of the relativistic stabilisation of the 6s orbital and the decreasing bond energy as the atoms increase in size so that the amount of energy released in forming two more bonds is not worth the high ionisation energies of the 6s electrons. It displays the +1 oxidation state that all the known alkali metals display, and thallium compounds with thallium in its +1 oxidation state closely resemble the corresponding potassium or silver compounds stoichiometrically due to the similar ionic radii of the Tl (164 pm), K (152 pm) and Ag (129 pm) ions. It was sometimes considered an alkali metal in continental Europe (but not in England) in the years immediately following its discovery, and was placed just after caesium as the sixth alkali metal in Dmitri Mendeleev's 1869 periodic table and Julius Lothar Meyer's 1868 periodic table. (Mendeleev's 1871 periodic table and Meyer's 1870 periodic table put thallium in its current position in the boron group and left the space below caesium blank.) However, thallium also displays the oxidation state +3, which no known alkali metal displays (although ununennium, the undiscovered seventh alkali metal, is predicted to possibly display the +3 oxidation state). The sixth alkali metal is now considered to be francium. While Tl is stabilised by the inert pair effect, this inert pair of 6s electrons is still able to participate chemically, so that these electrons are stereochemically active in aqueous solution. Additionally, the thallium halides (except TlF) are quite insoluble in water, and TlI has an unusual structure because of the presence of the stereochemically active inert pair in thallium.
Alkali metal
Because of the higher electronegativity of lithium, some of its compounds have a more covalent character. For example, lithium iodide (Li I) will dissolve in organic solvents, a property of most covalent compounds. Lithium fluoride (LiF) is the only alkali halide that is not soluble in water, and lithium hydroxide (LiOH) is the only alkali metal hydroxide that is not deliquescent.
Geochemistry
The chemical behavior of an atom – its affinity for other elements and the type of bonds it forms – is determined by the arrangement of electrons in orbitals, particularly the outermost (valence) electrons. These arrangements are reflected in the position of elements in the periodic table. Based on position, the elements fall into the broad groups of alkali metals, alkaline earth metals, transition metals, semi-metals (also known as metalloids), halogens, noble gases, lanthanides and actinides.
Alkali salt
These salts may include:
Alkalibacillus
The name "Alkalibacillus" derives from:New Latin noun "alkali" (from Arabic article "al", the; Arabic noun "qaliy", ashes of saltwort), alkali; Latin masculine gender noun "bacillus", rod; New Latin masculine gender noun "Alkalibacillus", bacillus living under alkaline conditions.
Alkali metal
Rubidium is approximately as abundant as zinc and more abundant than copper. It occurs naturally in the minerals leucite, pollucite, carnallite, zinnwaldite, and lepidolite, although none of these contain only rubidium and no other alkali metals. Caesium is more abundant than some commonly known elements, such as antimony, cadmium, tin, and tungsten, but is much less abundant than rubidium.
Plant defense against herbivory
Alkaloids are derived from various amino acids. Over 3000 known alkaloids exist, examples include nicotine, caffeine, morphine, cocaine, colchicine, ergolines, strychnine, and quinine. Alkaloids have pharmacological effects on humans and other animals. Some alkaloids can inhibit or activate enzymes, or alter carbohydrate and fat storage by inhibiting the formation phosphodiester bonds involved in their breakdown. Certain alkaloids bind to nucleic acids and can inhibit synthesis of proteins and affect DNA repair mechanisms. Alkaloids can also affect cell membrane and cytoskeletal structure causing the cells to weaken, collapse, or leak, and can affect nerve transmission. Although alkaloids act on a diversity of metabolic systems in humans and other animals, they almost uniformly invoke an aversively bitter taste.
Alkali metal
The alkali metals all have the same crystal structure (body-centred cubic) and thus the only relevant factors are the number of atoms that can fit into a certain volume and the mass of one of the atoms, since density is defined as mass per unit volume. The first factor depends on the volume of the atom and thus the atomic radius, which increases going down the group; thus, the volume of an alkali metal atom increases going down the group. The mass of an alkali metal atom also increases going down the group. Thus, the trend for the densities of the alkali metals depends on their atomic weights and atomic radii; if figures for these two factors are known, the ratios between the densities of the alkali metals can then be calculated. The resultant trend is that the densities of the alkali metals increase down the table, with an exception at potassium. Due to having the lowest atomic weight and the largest atomic radius of all the elements in their periods, the alkali metals are the least dense metals in the periodic table. Lithium, sodium, and potassium are the only three metals in the periodic table that are less dense than water: in fact, lithium is the least dense known solid at room temperature.
Alkali
The terms "base" and "alkali" are often used interchangeably, particularly outside the context of chemistry and chemical engineering.
Base (chemistry)
In water, by altering the autoionization equilibrium, bases yield solutions in which the hydrogen ion activity is lower than it is in pure water, i.e., the water has a pH higher than 7.0 at standard conditions. A soluble base is called an alkali if it contains and releases OH ions quantitatively. However, it is important to realize that basicity is not the same as alkalinity. Metal oxides, hydroxides, and especially alkoxides are basic, and counteranions of weak acids are weak bases.
Alkali metal
Hydrogen, like the alkali metals, has one valence electron and reacts easily with the halogens, but the similarities end there because of the small size of a bare proton H compared to the alkali metal cations. Its placement above lithium is primarily due to its electron configuration. It is sometimes placed above carbon due to their similar electronegativities or fluorine due to their similar chemical properties.
Alkylation
Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion or a carbene (or their equivalents). An alkyl group is a piece of a molecule with the general formula CH, where "n" is the integer depicting the number of carbons linked together. For example, a methyl group ("n" = 1, CH) is a fragment of a methane molecule (CH). Alkylating agents use selective alkylation by adding the desired aliphatic carbon chain to the previously chosen starting molecule. This is one of many known chemical syntheses. Alkyl groups can also be removed in a process known as dealkylation. Alkylating agents are often classified according to their nucleophilic or electrophilic character.
Alkali metal
Other "pseudo-alkali metals" include the alkylammonium cations, in which some of the hydrogen atoms in the ammonium cation are replaced by alkyl or aryl groups. In particular, the quaternary ammonium cations () are very useful since they are permanently charged, and they are often used as an alternative to the expensive Cs to stabilise very large and very easily polarisable anions such as . Tetraalkylammonium hydroxides, like alkali metal hydroxides, are very strong bases that react with atmospheric carbon dioxide to form carbonates. Furthermore, the nitrogen atom may be replaced by a phosphorus, arsenic, or antimony atom (the heavier nonmetallic pnictogens), creating a phosphonium () or arsonium () cation that can itself be substituted similarly; while stibonium () itself is not known, some of its organic derivatives are characterised.
Alkane
All alkanes are colorless. Alkanes with the lowest molecular weights are gasses, those of intermediate molecular weight are liquids, and the heaviest are waxy solids.
Alkaloid
Most plants contain several alkaloids. Their mixture is extracted first and then individual alkaloids are separated. Plants are thoroughly ground before extraction. Most alkaloids are present in the raw plants in the form of salts of organic acids. The extracted alkaloids may remain salts or change into bases. Base extraction is achieved by processing the raw material with alkaline solutions and extracting the alkaloid bases with organic solvents, such as 1,2-dichloroethane, chloroform, diethyl ether or benzene. Then, the impurities are dissolved by weak acids; this converts alkaloid bases into salts that are washed away with water. If necessary, an aqueous solution of alkaloid salts is again made alkaline and treated with an organic solvent. The process is repeated until the desired purity is achieved.
Alkali metal
The alkali metals can also react analogously with the heavier chalcogens (sulfur, selenium, tellurium, and polonium), and all the alkali metal chalcogenides are known (with the exception of francium's). Reaction with an excess of the chalcogen can similarly result in lower chalcogenides, with chalcogen ions containing chains of the chalcogen atoms in question. For example, sodium can react with sulfur to form the sulfide (NaS) and various polysulfides with the formula NaS ("x" from 2 to 6), containing the ions. Due to the basicity of the Se and Te ions, the alkali metal selenides and tellurides are alkaline in solution; when reacted directly with selenium and tellurium, alkali metal polyselenides and polytellurides are formed along with the selenides and tellurides with the and ions. They may be obtained directly from the elements in liquid ammonia or when air is not present, and are colourless, water-soluble compounds that air oxidises quickly back to selenium or tellurium. The alkali metal polonides are all ionic compounds containing the Po ion; they are very chemically stable and can be produced by direct reaction of the elements at around 300–400 °C.
Alkalinity
Alkalinity is typically reported as mg/L "as" CaCO. (The conjunction "as" is appropriate in this case because the alkalinity results from a mixture of ions but is reported "as if" all of this is due to CaCO.) This can be converted into milliEquivalents per Liter (mEq/L) by dividing by 50 (the approximate MW of CaCO/2).
Acid–base titration
Alkalimetry and acidimetry are a kind of volumetric analysis in which the fundamental reaction is a neutralization reaction. Alkalimetry is the specialized analytic use of acid-base titration to determine the concentration of a basic (synonymous to alkaline) substance. Acidimetry, sometimes spelled acidometry, is the same concept of specialized analytic acid-base titration, but for an acidic substance.
Alkali metal
Electronegativity is a chemical property that describes the tendency of an atom or a functional group to attract electrons (or electron density) towards itself. If the bond between sodium and chlorine in sodium chloride were covalent, the pair of shared electrons would be attracted to the chlorine because the effective nuclear charge on the outer electrons is +7 in chlorine but is only +1 in sodium. The electron pair is attracted so close to the chlorine atom that they are practically transferred to the chlorine atom (an ionic bond). However, if the sodium atom was replaced by a lithium atom, the electrons will not be attracted as close to the chlorine atom as before because the lithium atom is smaller, making the electron pair more strongly attracted to the closer effective nuclear charge from lithium. Hence, the larger alkali metal atoms (further down the group) will be less electronegative as the bonding pair is less strongly attracted towards them. As mentioned previously, francium is expected to be an exception.
Acid–base reaction
An acid–alkali reaction is a special case of an acid–base reaction, where the base used is also an alkali. When an acid reacts with an alkali salt (a metal hydroxide), the product is a metal salt and water. Acid–alkali reactions are also neutralization reactions.
Alkaloid
Alkaloids are a class of naturally occurring organic compounds that mostly contain basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar structure may also be termed alkaloids. In addition to carbon, hydrogen and nitrogen, alkaloids may also contain oxygen, sulfur and, more rarely, other elements such as chlorine, bromine, and phosphorus.
Alkali
The second subset of bases is also called an "Arrhenius base".
Alkali metal
Due to the great rarity of odd–odd nuclei, almost all the primordial isotopes of the alkali metals are odd–even (the exceptions being the light stable isotope lithium-6 and the long-lived radioisotope potassium-40). For a given odd mass number, there can be only a single beta-stable nuclide, since there is not a difference in binding energy between even–odd and odd–even comparable to that between even–even and odd–odd, leaving other nuclides of the same mass number (isobars) free to beta decay toward the lowest-mass nuclide. An effect of the instability of an odd number of either type of nucleons is that odd-numbered elements, such as the alkali metals, tend to have fewer stable isotopes than even-numbered elements. Of the 26 monoisotopic elements that have only a single stable isotope, all but one have an odd atomic number and all but one also have an even number of neutrons. Beryllium is the single exception to both rules, due to its low atomic number.
Alkali metal
Although francium is the heaviest alkali metal that has been discovered, there has been some theoretical work predicting the physical and chemical characteristics of the hypothetical heavier alkali metals. Being the first period 8 element, the undiscovered element ununennium (element 119) is predicted to be the next alkali metal after francium and behave much like their lighter congeners; however, it is also predicted to differ from the lighter alkali metals in some properties. Its chemistry is predicted to be closer to that of potassium or rubidium instead of caesium or francium. This is unusual as periodic trends, ignoring relativistic effects would predict ununennium to be even more reactive than caesium and francium. This lowered reactivity is due to the relativistic stabilisation of ununennium's valence electron, increasing ununennium's first ionisation energy and decreasing the metallic and ionic radii; this effect is already seen for francium. This assumes that ununennium will behave chemically as an alkali metal, which, although likely, may not be true due to relativistic effects. The relativistic stabilisation of the 8s orbital also increases ununennium's electron affinity far beyond that of caesium and francium; indeed, ununennium is expected to have an electron affinity higher than all the alkali metals lighter than it. Relativistic effects also cause a very large drop in the polarisability of ununennium. On the other hand, ununennium is predicted to continue the trend of melting points decreasing going down the group, being expected to have a melting point between 0 °C and 30 °C.
The stabilisation of ununennium's valence electron and thus the contraction of the 8s orbital cause its atomic radius to be lowered to 240 pm, very close to that of rubidium (247 pm), so that the chemistry of ununennium in the +1 oxidation state should be more similar to the chemistry of rubidium than to that of francium. On the other hand, the ionic radius of the Uue ion is predicted to be larger than that of Rb, because the 7p orbitals are destabilised and are thus larger than the p-orbitals of the lower shells. Ununennium may also show the +3 oxidation state, which is not seen in any other alkali metal, in addition to the +1 oxidation state that is characteristic of the other alkali metals and is also the main oxidation state of all the known alkali metals: this is because of the destabilisation and expansion of the 7p spinor, causing its outermost electrons to have a lower ionisation energy than what would otherwise be expected. Indeed, many ununennium compounds are expected to have a large covalent character, due to the involvement of the 7p electrons in the bonding.
Not as much work has been done predicting the properties of the alkali metals beyond ununennium. Although a simple extrapolation of the periodic table would put element 169, unhexennium, under ununennium, Dirac-Fock calculations predict that the next alkali metal after ununennium may actually be element 165, unhexpentium, which is predicted to have the electron configuration [Og] 5g 6f 7d 8s 8p 9s. Furthermore, this element would be intermediate in properties between an alkali metal and a group 11 element, and while its physical and atomic properties would be closer to the former, its chemistry may be closer to that of the latter. Further calculations show that unhexpentium would follow the trend of increasing ionisation energy beyond caesium, having an ionisation energy comparable to that of sodium, and that it should also continue the trend of decreasing atomic radii beyond caesium, having an atomic radius comparable to that of potassium. However, the 7d electrons of unhexpentium may also be able to participate in chemical reactions along with the 9s electron, possibly allowing oxidation states beyond +1, whence the likely transition metal behaviour of unhexpentium. Due to the alkali and alkaline earth metals both being s-block elements, these predictions for the trends and properties of ununennium and unhexpentium also mostly hold quite similarly for the corresponding alkaline earth metals unbinilium (Ubn) and unhexhexium (Uhh).
Alkali metal
Being the smallest alkali metal, lithium forms the widest variety of and most stable organometallic compounds, which are bonded covalently. Organolithium compounds are electrically non-conducting volatile solids or liquids that melt at low temperatures, and tend to form oligomers with the structure (RLi) where R is the organic group. As the electropositive nature of lithium puts most of the charge density of the bond on the carbon atom, effectively creating a carbanion, organolithium compounds are extremely powerful bases and nucleophiles. For use as bases, butyllithiums are often used and are commercially available. An example of an organolithium compound is methyllithium ((CHLi)), which exists in tetrameric ("x" = 4, tetrahedral) and hexameric ("x" = 6, octahedral) forms. Organolithium compounds, especially "n"-butyllithium, are useful reagents in organic synthesis, as might be expected given lithium's diagonal relationship with magnesium, which plays an important role in the Grignard reaction. For example, alkyllithiums and aryllithiums may be used to synthesise aldehydes and ketones by reaction with metal carbonyls. The reaction with nickel tetracarbonyl, for example, proceeds through an unstable acyl nickel carbonyl complex which then undergoes electrophilic substitution to give the desired aldehyde (using H as the electrophile) or ketone (using an alkyl halide) product.
Alkali metal
The smaller alkali metals tend to polarise the larger anions (the peroxide and superoxide) due to their small size. This attracts the electrons in the more complex anions towards one of its constituent oxygen atoms, forming an oxide ion and an oxygen atom. This causes lithium to form the oxide exclusively on reaction with oxygen at room temperature. This effect becomes drastically weaker for the larger sodium and potassium, allowing them to form the less stable peroxides. Rubidium and caesium, at the bottom of the group, are so large that even the least stable superoxides can form. Because the superoxide releases the most energy when formed, the superoxide is preferentially formed for the larger alkali metals where the more complex anions are not polarised. (The oxides and peroxides for these alkali metals do exist, but do not form upon direct reaction of the metal with oxygen at standard conditions.) In addition, the small size of the Li and O ions contributes to their forming a stable ionic lattice structure. Under controlled conditions, however, all the alkali metals, with the exception of francium, are known to form their oxides, peroxides, and superoxides. The alkali metal peroxides and superoxides are powerful oxidising agents. Sodium peroxide and potassium superoxide react with carbon dioxide to form the alkali metal carbonate and oxygen gas, which allows them to be used in submarine air purifiers; the presence of water vapour, naturally present in breath, makes the removal of carbon dioxide by potassium superoxide even more efficient. All the stable alkali metals except lithium can form red ozonides (MO) through low-temperature reaction of the powdered anhydrous hydroxide with ozone: the ozonides may be then extracted using liquid ammonia. They slowly decompose at standard conditions to the superoxides and oxygen, and hydrolyse immediately to the hydroxides when in contact with water. Potassium, rubidium, and caesium also form sesquioxides MO, which may be better considered peroxide disuperoxides, .
Alkali metal
The production of pure alkali metals is somewhat complicated due to their extreme reactivity with commonly used substances, such as water. From their silicate ores, all the stable alkali metals may be obtained the same way: sulfuric acid is first used to dissolve the desired alkali metal ion and aluminium(III) ions from the ore (leaching), whereupon basic precipitation removes aluminium ions from the mixture by precipitating it as the hydroxide. The remaining insoluble alkali metal carbonate is then precipitated selectively; the salt is then dissolved in hydrochloric acid to produce the chloride. The result is then left to evaporate and the alkali metal can then be isolated. Lithium and sodium are typically isolated through electrolysis from their liquid chlorides, with calcium chloride typically added to lower the melting point of the mixture. The heavier alkali metals, however, is more typically isolated in a different way, where a reducing agent (typically sodium for potassium and magnesium or calcium for the heaviest alkali metals) is used to reduce the alkali metal chloride. The liquid or gaseous product (the alkali metal) then undergoes fractional distillation for purification. Most routes to the pure alkali metals require the use of electrolysis due to their high reactivity; one of the few which does not is the pyrolysis of the corresponding alkali metal azide, which yields the metal for sodium, potassium, rubidium, and caesium and the nitride for lithium.
Leblanc process
Soda ash (sodium carbonate) and potash (potassium carbonate), collectively termed "alkali", are vital chemicals in the glass, textile, soap, and paper industries. The traditional source of alkali in western Europe had been potash obtained from wood ashes. However, by the 13th century, deforestation had rendered this means of production uneconomical, and alkali had to be imported. Potash was imported from North America, Scandinavia, and Russia, where large forests still stood. Soda ash was imported from Spain and the Canary Islands, where it was produced from the ashes of glasswort plants (called barilla ashes in Spain), or imported from Syria. The soda ash from glasswort plant ashes was mainly a mixture of sodium carbonate and potassium carbonate. In addition in Egypt, naturally occurring sodium carbonate, the mineral natron, was mined from dry lakebeds. In Britain, the only local source of alkali was from kelp, which washed ashore in Scotland and Ireland.
Alkali salt
Rather than being neutral (as some other salts), alkali salts are bases as their name suggests. What makes these compounds basic is that the conjugate base from the weak acid hydrolyzes to form a basic solution. In sodium carbonate, for example, the carbonate from the carbonic acid hydrolyzes to form a basic solution. The chloride from the hydrochloric acid in sodium chloride does not hydrolyze, though, so sodium chloride is not basic.
Alkali metal
The alkali metals form complete series of compounds with all usually encountered anions, which well illustrate group trends. These compounds can be described as involving the alkali metals losing electrons to acceptor species and forming monopositive ions. This description is most accurate for alkali halides and becomes less and less accurate as cationic and anionic charge increase, and as the anion becomes larger and more polarisable. For instance, ionic bonding gives way to metallic bonding along the series NaCl, NaO, NaS, NaP, NaAs, NaSb, NaBi, Na.
Glass
The alkali metal ions are small and mobile; their presence in glass allows a degree of electrical conductivity, especially in molten state or at high temperature. Their mobility decreases the chemical resistance of the glass, allowing leaching by water and facilitating corrosion. Alkaline earth ions, with their two positive charges and requirement for two non-bridging oxygen ions to compensate for their charge, are much less mobile themselves and also hinder diffusion of other ions, especially the alkalis. The most common commercial glass types contain both alkali and alkaline earth ions (usually sodium and calcium), for easier processing and satisfying corrosion resistance. Corrosion resistance of glass can be increased by dealkalization, removal of the alkali ions from the glass surface by reaction with sulfur or fluorine compounds. Presence of alkaline metal ions has also detrimental effect to the loss tangent of the glass, and to its electrical resistance; glass manufactured for electronics (sealing, vacuum tubes, lamps ...) have to take this in account.
Alkalide
Alkali metals form many well-known stable salts. Sodium chloride (common table salt), NaCl, illustrates the usual role of an alkali metal such as sodium. In the empirical formula for this ionic compound, the positively charged sodium ion balanced by a negatively charged chloride ion. The traditional explanation for stable Na is that the loss of one electron from elemental sodium to produce a cation with charge of +1 produces a stable closed-shell electron configuration.
Alkali
There are various more specific definitions for the concept of an alkali. Alkalis are usually defined as a subset of the bases. One of two subsets is commonly chosen.