What elements are in the chalcogen group?
Hydrogen chalcogenide
Hydrogen chalcogenides (also chalcogen hydrides or hydrogen chalcides) are binary compounds of hydrogen with chalcogen atoms (elements of group 16: oxygen, sulfur, selenium, tellurium, and polonium). Water, the first chemical compound in this series, contains one oxygen atom and two hydrogen atoms, and is the most common compound on the Earth's surface.
Gas
The only chemical elements that are stable diatomic homonuclear molecules at STP are hydrogen (H), nitrogen (N), oxygen (O), and two halogens: fluorine (F) and chlorine (Cl). When grouped together with the monatomic noble gases – helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn) – these gases are called "elemental gases".
Goldschmidt classification
The most metallic chalcophile elements (of the copper, zinc and boron groups) may mix to some degree with iron in the Earth's core. They are not likely to be depleted on Earth as a whole relative to their solar abundances since they do not form volatile hydrides. Zinc and gallium are somewhat "lithophile" in nature because they often occur in silicate or related minerals and form quite strong bonds with oxygen. Gallium, notably, is sourced mainly from bauxite, an aluminum hydroxide ore in which gallium ion substitutes for chemically similar aluminum.
Indium chalcogenides
The indium chalcogenides include all compounds of indium with the chalcogen elements, oxygen, sulfur, selenium and tellurium. (Polonium is excluded as little is known about its compounds with indium). The best-characterised compounds are the In(III) and In(II) chalcogenides e.g. the sulfides InS and InS.
This group of compounds has attracted a lot of research attention because they include semiconductors, photovoltaics and phase-change materials. In many applications indium chalcogenides are used as the basis of ternary and quaternary compounds such as indium tin oxide, ITO and copper indium gallium selenide, CIGS.
Hexafluoride
Seventeen elements are known to form binary hexafluorides. Nine of these elements are transition metals, three are actinides, four are chalcogens, and one is a noble gas. Most hexafluorides are molecular compounds with low melting and boiling points. Four hexafluorides (S, Se, Te, and W) are gases at room temperature (25 °C) and a pressure of 1 atm, two are liquids (Re, Mo), and the others are volatile solids. The group 6, chalcogen, and noble gas hexafluorides are colourless, but the other hexafluorides have colours ranging from white, through yellow, orange, red, brown, and grey, to black.
Chalcogenide
The chalcogen is assigned positive oxidation states for the halides, nitrides, and oxides.
Nickelocene
Ni(CH) belongs to a group of organometallic compounds called metallocenes. Metallocenes usually adopt structures in which a metal ion is sandwiched between two parallel cyclopentadienyl (Cp) rings. In the solid-state, the molecule has D symmetry, wherein the two rings are eclipsed.
Chalcogen
Chalcophile elements are those that remain on or close to the surface because they combine readily with chalcogens other than oxygen, forming compounds which do not sink into the core. Chalcophile ("chalcogen-loving") elements in this context are those metals and heavier nonmetals that have a low affinity for oxygen and prefer to bond with the heavier chalcogen sulfur as sulfides. Because sulfide minerals are much denser than the silicate minerals formed by lithophile elements, chalcophile elements separated below the lithophiles at the time of the first crystallisation of the Earth's crust. This has led to their depletion in the Earth's crust relative to their solar abundances, though this depletion has not reached the levels found with siderophile elements.
Chalcogenide glass
Although the electronic structural transitions relevant to both optical discs and PC-RAM were featured strongly, contributions from ions were not considered—even though amorphous chalcogenides can have significant ionic conductivities. At Euromat 2005, however, it was shown that ionic transport can also be useful for data storage in a solid chalcogenide electrolyte. At the nanoscale, this electrolyte consists of crystalline metallic islands of silver selenide (AgSe) dispersed in an amorphous semiconducting matrix of germanium selenide (GeSe).
Chalcogen bond
Any electron donor can donate electrons into the σ-hole of a bonded chalcogen, including halogen anions, amines, and π electrons (such as benzene). Similar to halogen bonding, chalcogen bonding can occur between two chalcogens, resulting in a chalcogen-chalcogen bond. Non-covalent interactions are well characterized by Bader's atoms in molecules (AIM) model which defines a bond as any bond-critical point (BCP) existing between two nuclei. This can be understood simply as a saddle point on an electron density map of a molecule. Hydrogen and halogen bonds are both well characterized by this method. The same analysis has been performed on chalcogen bonds, as shown below. The BCP's between S and Cl in these molecules are evidence of the non-covalent interactions, in this case chalcogen-halogen bonds.
Another method used to evaluate chalcogen bonding specifically and a wide range of bonding generally is natural bond orbital (NBO) analysis. NBO analysis distinguishes between covalent, Lewis-type bonding interactions and non-covalent, non-Lewis bonding interaction. The chalcogen bond will be evaluated based on the natural population of the n → σ* orbital. A higher population of this orbital should then also be reflected in changes in the geometry.
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.
Chalcogen
Selenium's oxidation states are −2, +4, and +6. Selenium, like most chalcogens, bonds with oxygen. There are some organic selenium compounds, such as selenoproteins. Tellurium's oxidation states are −2, +2, +4, and +6. Tellurium forms the oxides tellurium monoxide, tellurium dioxide, and tellurium trioxide. Polonium's oxidation states are +2 and +4.
There are many acids containing chalcogens, including sulfuric acid, sulfurous acid, selenic acid, and telluric acid. All hydrogen chalcogenides are toxic except for water. Oxygen ions often come in the forms of oxide ions (), peroxide ions (), and hydroxide ions (). Sulfur ions generally come in the form of sulfides (), sulfites (), sulfates (), and thiosulfates (). Selenium ions usually come in the form of selenides () and selenates (). Tellurium ions often come in the form of tellurates (). Molecules containing metal bonded to chalcogens are common as minerals. For example, pyrite (FeS) is an iron ore, and the rare mineral calaverite is the ditelluride (Au, Ag)Te.
Chalcogen
The four lightest chalcogens (oxygen, sulfur, selenium, and tellurium) are all primordial elements on Earth. Sulfur and oxygen occur as constituent copper ores and selenium and tellurium occur in small traces in such ores. Polonium forms naturally after the decay of other elements, even though it is not primordial. Livermorium does not occur naturally at all.
Chalconoid
Chalconoids Greek: χαλκός "khalkós", "copper", due to its color), also known as "chalcones", are natural phenols related to chalcone. They form the central core for a variety of important biological compounds.
Periodic table
Hydrogen's chemical properties are not very close to those of the alkali metals, which occupy group 1. On this basis it is sometimes placed elsewhere. A common alternative is at the top of group 17 given hydrogen's strictly univalent and largely non-metallic chemistry, and the strictly univalent and non-metallic chemistry of fluorine (the element otherwise at the top of group 17). Sometimes, to show hydrogen has properties corresponding to both those of the alkali metals and the halogens, it is shown at the top of the two columns simultaneously. Another suggestion is above carbon in group 14: placed that way, it fits well into the trends of increasing ionization potential values and electron affinity values, and is not too far from the electronegativity trend, even though hydrogen cannot show the tetravalence characteristic of the heavier group 14 elements. Finally, hydrogen is sometimes placed separately from any group; this is based on its general properties being different from those of the elements in any other group. The other period 1 element, helium, is sometimes placed separately from any group as well. The property that distinguishes helium from the rest of the noble gases (even though the extraordinary inertness of helium is extremely close to that of neon and argon) is that in its closed electron shell, helium has only two electrons in the outermost electron orbital, while the rest of the noble gases have eight.
Hallucinogen
Almost all hallucinogens contain nitrogen and are therefore classified as alkaloids. THC and salvinorin A are exceptions. Many hallucinogens have chemical structures similar to those of human neurotransmitters, such as serotonin, and temporarily modify the action of neurotransmitters and/or receptor sites.
Livermorium
Livermorium is projected to be the fourth member of the 7p series of chemical elements and the heaviest member of group 16 in the periodic table, below polonium. While it is the least theoretically studied of the 7p elements, its chemistry is expected to be quite similar to that of polonium. The group oxidation state of +6 is known for all the chalcogens apart from oxygen which lacks available d-orbitals for expansion of its octet and is itself one of the strongest oxidizing agents among the chemical elements. Oxygen is thus limited to a maximum +2 state, exhibited in the fluoride OF. The +4 state is known for sulfur, selenium, tellurium, and polonium, undergoing a shift in stability from reducing for sulfur(IV) and selenium(IV) through being the most stable state for tellurium(IV) to being oxidizing in polonium(IV). This suggests a decreasing stability for the higher oxidation states as the group is descended due to the increasing importance of relativistic effects, especially the inert pair effect. The most stable oxidation state of livermorium should thus be +2, with a rather unstable +4 state. The +2 state should be about as easy to form as it is for beryllium and magnesium, and the +4 state should only be achieved with strongly electronegative ligands, such as in livermorium(IV) fluoride (LvF). The +6 state should not exist at all due to the very strong stabilization of the 7s electrons, making the valence core of livermorium only four electrons. The lighter chalcogens are also known to form a −2 state as oxide, sulfide, selenide, telluride, and polonide; due to the destabilization of livermorium's 7p subshell, the −2 state should be very unstable for livermorium, whose chemistry should be essentially purely cationic, though the larger subshell and spinor energy splittings of livermorium as compared to polonium should make Lv slightly more stable than expected.
Chemistry: A Volatile History
Mendeleev's table reveals the relationship between all the elements in their order:Notice carbon and silicon are in Group IV and the volatile gases fluorine, chlorine and bromine are in Group VII.
Spinel group
The spinels are any of a class of minerals of general formulation which crystallise in the cubic (isometric) crystal system, with the X anions (typically chalcogens, like oxygen and sulfur) arranged in a cubic close-packed lattice and the cations A and B occupying some or all of the octahedral and tetrahedral sites in the lattice. Although the charges of A and B in the prototypical spinel structure are +2 and +3, respectively (), other combinations incorporating divalent, trivalent, or tetravalent cations, including magnesium, zinc, iron, manganese, aluminium, chromium, titanium, and silicon, are also possible. The anion is normally oxygen; when other chalcogenides constitute the anion sublattice the structure is referred to as a thiospinel.
Moscovium
In the periodic table, moscovium is a member of group 15, the pnictogens, below nitrogen, phosphorus, arsenic, antimony, and bismuth. Every previous pnictogen has five electrons in its valence shell, forming a valence electron configuration of nsnp. In moscovium's case, the trend should be continued and the valence electron configuration is predicted to be 7s7p; therefore, moscovium will behave similarly to its lighter congeners in many respects. However, notable differences are likely to arise; a largely contributing effect is the spin–orbit (SO) interaction—the mutual interaction between the electrons' motion and spin. It is especially strong for the superheavy elements, because their electrons move much faster than in lighter atoms, at velocities comparable to the speed of light. In relation to moscovium atoms, it lowers the 7s and the 7p electron energy levels (stabilizing the corresponding electrons), but two of the 7p electron energy levels are stabilized more than the other four. The stabilization of the 7s electrons is called the inert pair effect, and the effect "tearing" the 7p subshell into the more stabilized and the less stabilized parts is called subshell splitting. Computation chemists see the split as a change of the second (azimuthal) quantum number "l" from 1 to and for the more stabilized and less stabilized parts of the 7p subshell, respectively. For many theoretical purposes, the valence electron configuration may be represented to reflect the 7p subshell split as 7s7p7p. These effects cause moscovium's chemistry to be somewhat different from that of its lighter congeners.
Djurleite
The chalcocite group is a group of closely related copper sulfides, with the formulae:
Chalcogenide
Chalcogen derivatives are known for all of the main group elements except the noble gases. Usually, their stoichiometries follow the classical valence trends, e.g. SiS, BS, SbS. Many exceptions exist however, e.g. PS and SN. The structures of many of main group materials are dictated, not by close packing, but by directional covalent bonding.
Chalcogen
There is a very large number of metal chalcogenides. One of the more recent discoveries in this group of compounds is RbTe. There are also compounds in which alkali metals and transition metals such as the fourth period transition metals except for copper and zinc. In highly metal-rich metal chalcogenides, such as LuTe and LuTe have domains of the metal's crystal lattice containing chalcogen atoms. While these compounds do exist, analogous chemicals that contain lanthanum, praseodymium, gadolinium, holmium, terbium, or ytterbium have not been discovered, as of 2008. The boron group metals aluminum, gallium, and indium also form bonds to chalcogens. The Ti ion forms chalcogenide dimers such as TiTlSe. Metal chalcogenide dimers also occur as lower tellurides, such as ZrTe.
Chalcogenide glass
Chalcogenide glass (pronounced hard "ch" as in "chemistry") is a glass containing one or more chalcogens (sulfur, selenium and tellurium, but excluding oxygen). Such glasses are covalently bonded materials and may be classified as covalent network solids. Polonium is also a chalcogen but is not used because of its strong radioactivity. Chalcogenide materials behave rather differently from oxides, in particular their lower band gaps contribute to very dissimilar optical and electrical properties.
Chalcone synthase
Chalcone synthase or naringenin-chalcone synthase (CHS) is an enzyme ubiquitous to higher plants and belongs to a family of polyketide synthase enzymes (PKS) known as type III PKS. Type III PKSs are associated with the production of chalcones, a class of organic compounds found mainly in plants as natural defense mechanisms and as synthetic intermediates. CHS was the first type III PKS to be discovered. It is the first committed enzyme in flavonoid biosynthesis.
The enzyme catalyzes the conversion of 4-coumaroyl-CoA and malonyl-CoA to naringenin chalcone.
Hydrogen isotope biogeochemistry
Another group of molecules frequently used in paleoreconstructions are alkenones, long-chain largely unsaturated lipids produced exclusively by coccolithophores. Coccolithophores are marine haptophyte algae, and include the globally iconic species "Emiliania huxleyi", one of the main CaCO producers in the ocean. The δD values of alkenones are highly correlated to the δD values of sea water, and therefore can be used to reconstruct paleoenvironmental properties that constrain the isotopic composition of sea water. The most notable reconstruction that alkenone δD values are applied to is the salinity of ancient oceans.Both the δD values of sea water and the fractionations associated with hyptophyte biochemistry (ε) are fairly well understood, so alkenones can be readily used to observe the secondary effect of salinity on δD. There is a well established positive linear correlation between salinity and ε, on the order of a ~3‰ change in fractionation per salinity unit. Hypothesized mechanisms for this effect include enrichment of D in intracellular water due to reduced exchange with extracellular water at higher salinity, removal of H from intracellular water due to increased production of solutes to maintain osmotic pressure at higher salinity, and lower haptophyte growth rates at higher salinity
Chalcogen
Tellurium was first discovered in 1783 by Franz Joseph Müller von Reichenstein. He discovered tellurium in a sample of what is now known as calaverite. Müller assumed at first that the sample was pure antimony, but tests he ran on the sample did not agree with this. Muller then guessed that the sample was bismuth sulfide, but tests confirmed that the sample was not that. For some years, Muller pondered the problem. Eventually he realized that the sample was gold bonded with an unknown element. In 1796, Müller sent part of the sample to the German chemist Martin Klaproth, who purified the undiscovered element. Klaproth decided to call the element tellurium after the Latin word for earth.
Binary compounds of hydrogen
Elements in group 13 to 17 (p-block) form covalent hydrides (or nonmetal hydrides). In group 12 zinc hydride is a common chemical reagent but cadmium hydride and mercury hydride are very unstable and esoteric. In group 13 boron hydrides exist as a highly reactive monomer BH, as an adduct for example ammonia borane or as dimeric diborane and as a whole group of BH cluster compounds. Alane (AlH) is a polymer. Gallium exists as the dimer digallane. Indium hydride is only stable below . Not much is known about the final group 13 hydride, thallium hydride.
Chalcogen
Chalcogens also form compounds with halogens known as chalcohalides. Such compounds are known as chalcogen halides. The majority of simple chalcogen halides are well-known and widely used as chemical reagents. However, more complicated chalcogen halides, such as sulfenyl, sulfonyl, and sulfuryl halides, are less well known to science. Out of the compounds consisting purely of chalcogens and halogens, there are a total of 13 chalcogen fluorides, nine chalcogen chlorides, eight chalcogen bromides, and six chalcogen iodides that are known. The heavier chalcogen halides often have significant molecular interactions. Sulfur fluorides with low valences are fairly unstable and little is known about their properties. However, sulfur fluorides with high valences, such as sulfur hexafluoride, are stable and well-known. Sulfur tetrafluoride is also a well-known sulfur fluoride. Certain selenium fluorides, such as selenium difluoride, have been produced in small amounts. The crystal structures of both selenium tetrafluoride and tellurium tetrafluoride are known. Chalcogen chlorides and bromides have also been explored. In particular, selenium dichloride and sulfur dichloride can react to form organic selenium compounds. Dichalcogen dihalides, such as SeCl also are known to exist. There are also mixed chalcogen-halogen compounds. These include SeSX, with X being chlorine or bromine. Such compounds can form in mixtures of sulfur dichloride and selenium halides. These compounds have been fairly recently structurally characterized, as of 2008. In general, diselenium and disulfur chlorides and bromides are useful chemical reagents. Chalcogen halides with attached metal atoms are soluble in organic solutions. One example of such a compound is MoSCl. Unlike selenium chlorides and bromides, selenium iodides have not been isolated, as of 2008, although it is likely that they occur in solution. Diselenium diiodide, however, does occur in equilibrium with selenium atoms and iodine molecules. Some tellurium halides with low valences, such as TeCl and TeBr, form polymers when in the solid state. These tellurium halides can be synthesized by the reduction of pure tellurium with superhydride and reacting the resulting product with tellurium tetrahalides. Ditellurium dihalides tend to get less stable as the halides become lower in atomic number and atomic mass. Tellurium also forms iodides with even fewer iodine atoms than diiodies. These include TeI and TeI. These compounds have extended structures in the solid state. Halogens and chalcogens can also form halochalcogenate anions.
Celsian
Celsian is a barium feldspar with a chemical composition BaAlSiO. It forms part of the feldspar group and belongs to the celsian-hyalophane series and the celsian-orthoclase series. It has some resemblance to anorthite, and it has four distinct polymorphs.
The essential elements are Si,Al,O and Ba. Some common impurities in the mineral are Fe, Ti, Mg, K and Ca. Celsian is stable from room temperature up to 1590 °C ( Lin and Foster,1968). The most common trace elements are potassium and calcium, in an analysis of the approximate chemical composition of celsian the following wt% were found: 
• SiO—35.1 
• AlO---26.8
• BaO----35.8
• KO-----2.3
Total:100.0 (Newham and Megaw,1960).
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.
Aerogel
Chalcogel is an aerogel made of chalcogens (the column of elements on the periodic table beginning with oxygen) such as sulfur, selenium and other elements. Metals less expensive than platinum have been used in its creation.
Chalcedony
Chalcedony () is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic. Chalcedony's standard chemical structure (based on the chemical structure of quartz) is SiO (silicon dioxide).
Hydrogen chalcogenide
It is possible for two different chalcogen atoms to share a dichalcogenide, as in hydrogen thioperoxide (HSO); more well-known compounds of similar description include sulfuric acid (HSO).
Group 14 hydride
Alongside hydrogen, carbon can form compounds with the chemically similar halogens, forming haloalkanes. The simplest of this series, the halomethanes, contain compounds such as dichloromethane and iodoform. Other such important chemicals include vinyl chloride, which is used in the production of PVC.
I-III-VI semiconductors
I-III-VI semiconductors are solid semiconducting materials that contain three or more chemical elements belonging to groups I, III and VI of the periodic table. They usually involve two metals and one chalcogen. Some of these materials have a direct bandgap, E, of ~ 1.5 eV, which makes them efficient absorbers of sunlight and thus potential solar cell materials. A fourth element is often added to a I-III-VI material to tune the bandgap for maximum solar cell efficiency. A representative example is copper indium gallium selenide (CuInGaSe, E = 1.7–1.0 eV for x = 0–1), which is used in copper indium gallium selenide solar cells.
Chalcone
Chalcone is an aromatic ketone and an enone that forms the central core for a variety of important biological compounds, which are known collectively as chalcones or chalconoids. Alternative names for chalcone include benzylideneacetophenone, phenyl styryl ketone, benzalacetophenone, "β"-phenylacrylophenone, "γ"-oxo-"α","γ"-diphenyl-"α"-propylene, and "α"-phenyl-"β"-benzoylethylene.
Haloketone
A haloketone in organic chemistry is a functional group consisting of a ketone group or more generally a carbonyl group with an α-halogen substituent. The general structure is RR'C(X)C(=O)R where R is an alkyl or aryl residue and X any one of the halogens. The preferred conformation of a haloketone is that of a cisoid with the halogen and carbonyl sharing the same plane as the steric hindrance with the carbonyl alkyl group is generally larger.Efforts are reported in asymmetric synthesis of halocarbonyls through organocatalysis. In one study an acid chloride is converted into an α-halo-ester with a strong base (sodium hydride), a bromine donor and an organocatalyst based on proline and quinine:
Livermorium
In the periodic table, it is a p-block transactinide element. It is a member of the 7th period and is placed in group 16 as the heaviest chalcogen, although it has not been confirmed to behave as the heavier homologue to the chalcogen polonium. Livermorium is calculated to have some similar properties to its lighter homologues (oxygen, sulfur, selenium, tellurium, and polonium), and be a post-transition metal, although it should also show several major differences from them.
Group 12 element
Although copernicium is the heaviest known group 12 element, there has been some theoretical work regarding possible heavier group 12 elements. Although a simple extrapolation of the periodic table would put element 162, unhexbium (Uhb), under copernicium, relativistic Dirac-Fock calculations predict that the next group 12 element after copernicium should actually be element 164, unhexquadium (Uhq), which is predicted to have an electron configuration of [Og] 5g 6f 7d 8s 8p. The 8s and 8p orbitals are predicted to be so strongly stabilized relativistically that they become core electrons and do not participate in chemical reactions, unlike the earlier group 12 elements where the s electrons behave as valence electrons. However, the 9s and 9p levels are expected to be readily available for hybridization and bonding, so that unhexquadium should still behave chemically like a normal transition metal. Calculations predict that the 7d electrons of unhexquadium should participate very readily in chemical reactions, so that unhexquadium should be able to show stable +6 and +4 oxidation states in addition to the normal +2 state in aqueous solutions with strong ligands. Unhexquadium should thus be able to form compounds like Uhq(CO), Uhq(PF) (both tetrahedral), and (linear), which is very different behavior from that of lead, which unhexquadium would be a heavier homologue of if not for relativistic effects. Nevertheless, the divalent state would be the main one in aqueous solution, and unhexquadium(II) should behave more similarly to lead than unhexquadium(IV) and unhexquadium(VI).
Chalconoid
Chalcones are aromatic ketones with two phenyl rings that are also intermediates in the synthesis of many biological compounds. The closure of hydroxychalcones causes the formation of the flavonoid structure. Flavonoids are substances in the plant secondary metabolism with an array of biological activities.
Chalcogenide
In contrast to classical metal dichalcogenides, iron pyrite, a common mineral, is usually described as consisting of Fe and the persulfido anion S. The sulfur atoms within the disulfido dianion are bound together via a short S-S bond. "Late" transition metal disulfides (Mn, Fe, Co, Ni) almost always adopt the pyrite or the related marcasite motif, in contrast to early metals (V, Ti, Mo, W) which adopt 4+ oxidation state with two chalcogenide dianions.
Metallate
Typically, the metal will be one of the transition elements and the ligand will be oxygen or another chalcogenide or a cyanide group (though others are known). The chalcogenide metallates are known as oxometallates, thiometallates, selenometallates and tellurometallates; the cyanide metallates are known as cyanometallates.
Copernicium
Because the lighter group 12 elements often occur as chalcogenide ores, experiments were conducted in 2015 to attempt to deposit copernicium atoms on a selenium surface to form copernicium selenide, CnSe. Reaction of copernicium atoms with trigonal selenium to form a selenide were observed, with Δ"H"(t-Se) > 48 kJ/mol, with the kinetic hindrance towards selenide formation being lower for copernicium than for mercury. This was unexpected as the stability of the group 12 selenides tends to decrease down the group from ZnSe to HgSe, while it increases down the group for the group 14 selenides from GeSe to PbSe.
Goldschmidt classification
Chalcophile elements are those that remain on or close to the surface because they combine readily with sulfur and/or some other chalcogen other than oxygen, forming compounds which do not sink into the core.
Chalcogen
Oxygen's most common allotrope is diatomic oxygen, or O, a reactive paramagnetic molecule that is ubiquitous to aerobic organisms and has a blue color in its liquid state. Another allotrope is O, or ozone, which is three oxygen atoms bonded together in a bent formation. There is also an allotrope called tetraoxygen, or O, and six allotropes of solid oxygen including "red oxygen", which has the formula O.
Chalcogen
Selenium has at least five known allotropes. The gray allotrope, commonly referred to as the "metallic" allotrope, despite not being a metal, is stable and has a hexagonal crystal structure. The gray allotrope of selenium is soft, with a Mohs hardness of 2, and brittle. The four other allotropes of selenium are metastable. These include two monoclinic red allotropes and two amorphous allotropes, one of which is red and one of which is black. The red allotrope converts to the red allotrope in the presence of heat. The gray allotrope of selenium is made from spirals on selenium atoms, while one of the red allotropes is made of stacks of selenium rings (Se).
Cobaltocene
Co(CH) belongs to a group of organometallic compounds called metallocenes or sandwich compounds. Cobaltocene has 19 valence electrons, one more than usually found in organotransition metal complexes such as its very stable relative ferrocene. (See 18-electron rule.) This additional electron occupies an orbital that is antibonding with respect to the Co–C bonds. Consequently, the Co–C distances are slightly longer than the Fe–C bonds in ferrocene. Many chemical reactions of Co(CH) are characterized by its tendency to lose this "extra" electron, yielding an 18-electron cation known as cobaltocenium:
Group 6 element
Unlike other groups, the members of this family do not show patterns in its electron configuration, as two lighter members of the group are exceptions from the Aufbau principle:
Most of the chemistry has been observed only for the first three members of the group. The chemistry of seaborgium is not very established and therefore the rest of the section deals only with its upper neighbors in the periodic table. The elements in the group, like those of groups 7—11, have high melting points, and form volatile compounds in higher oxidation states. All the elements of the group are relatively nonreactive metals with a high melting points (1907 °C, 2477 °C, 3422 °C); that of tungsten is the highest of all metals. The metals form compounds in different oxidation states: chromium forms compounds in all states from −2 to +6: disodium pentacarbonylchromate, disodium decacarbonyldichromate, bis(benzene)chromium, tripotassium pentanitrocyanochromate, chromium(II) chloride, chromium(III) oxide, chromium(IV) chloride, potassium tetraperoxochromate(V), and chromium(VI) dichloride dioxide; the same is also true for molybdenum and tungsten, but the stability of the +6 state grows down the group. Depending on oxidation states, the compounds are basic, amphoteric, or acidic; the acidity grows with the oxidation state of the metal.
Cobalt
The principal chalcogenides of cobalt include the black cobalt(II) sulfides, CoS, which adopts a pyrite-like structure, and cobalt(III) sulfide (CoS).
Goldschmidt classification
However, because they formed volatile hydrides on the primitive Earth when the controlling redox reaction was the oxidation or reduction of hydrogen, the less metallic chalcophile elements are strongly depleted on Earth as a whole relative to cosmic abundances. This is most especially true of the chalcogens selenium and tellurium (which formed volatile hydrogen selenide and hydrogen telluride, respectively), which for this reason are among the rarest elements found in the Earth's crust (to illustrate, tellurium is only about as abundant as platinum).
Chalcogenide
Metal monochalcogenides have the formula ME, where M = a transition metal and E = S, Se, Te. They typically crystallize in one of two motifs, named after the corresponding forms of zinc sulfide. In the zinc blende structure, the sulfide atoms pack in a cubic symmetry and the Zn ions occupy half of the tetrahedral holes. The result is a diamondoid framework. The main alternative structure for the monochalcogenides is the wurtzite structure wherein the atom connectivities are similar (tetrahedral), but the crystal symmetry is hexagonal. A third motif for metal monochalcogenide is the nickel arsenide lattice, where the metal and chalcogenide each have octahedral and trigonal prismatic coordination, respectively. This motif is commonly subject to nonstoichiometry.
Hydrogen chalcogenide
The most important series, including water, has the chemical formula HX, with X representing any chalcogen. They are therefore triatomic. They take on a bent structure and as such are polar molecules. Water is an essential compound to life on Earth today, covering 70.9% of the planet's surface. The other hydrogen chalcogenides are usually extremely toxic, and have strong unpleasant scents usually resembling rotting eggs or vegetables. Hydrogen sulfide is a common product of decomposition in oxygen-poor environments and as such is one chemical responsible for the smell of flatulence. It is also a volcanic gas. Despite its toxicity, the human body intentionally produces it in small enough doses for use as a signaling molecule.
Block (periodic table)
The s-block is on the left side of the periodic table and includes elements from the first two columns, the alkali metals (group 1) and alkaline earth metals (group 2), plus hydrogen and helium. Helium can be placed in the second group of s block as well as the 18th group of p-block, but most scientists consider it to rest at the top of group 18 i.e. above neon (atomic number 10) as it has many properties similar to the group 18 elements. General valance configration is ns1-2
Livermorium
In the periodic table, livermorium is a member of group 16, the chalcogens, in the periodic table, below oxygen, sulfur, selenium, tellurium, and polonium. Every previous chalcogen has six electrons in its valence shell, forming a valence electron configuration of nsnp. In livermorium's case, the trend should be continued and the valence electron configuration is predicted to be 7s7p; therefore, livermorium will have some similarities to its lighter congeners. Differences are likely to arise; a large contributing effect is the spin–orbit (SO) interaction—the mutual interaction between the electrons' motion and spin. It is especially strong for the superheavy elements, because their electrons move much faster than in lighter atoms, at velocities comparable to the speed of light. In relation to livermorium atoms, it lowers the 7s and the 7p electron energy levels (stabilizing the corresponding electrons), but two of the 7p electron energy levels are stabilized more than the other four. The stabilization of the 7s electrons is called the inert pair effect, and the effect "tearing" the 7p subshell into the more stabilized and the less stabilized parts is called subshell splitting. Computation chemists see the split as a change of the second (azimuthal) quantum number "l" from 1 to and for the more stabilized and less stabilized parts of the 7p subshell, respectively: the 7p subshell acts as a second inert pair, though not as inert as the 7s electrons, while the 7p subshell can easily participate in chemistry. For many theoretical purposes, the valence electron configuration may be represented to reflect the 7p subshell split as 7s7p7p.
Chalcogenide glass
The physical properties of chalcogenide glasses (high refractive index, low phonon energy, high nonlinearity) also make them ideal for incorporation into lasers, planar optics, photonic integrated circuits, and other active devices especially if doped with rare-earth element ions. Some chalcogenide glasses exhibit several non-linear optical effects such as photon-induced refraction, and electron-induced permittivity modification
Abundance of the chemical elements
By mass, human cells consist of 65–90% water (HO), and a significant portion of the remainder is composed of carbon-containing organic molecules. Oxygen therefore contributes a majority of a human body's mass, followed by carbon. Almost 99% of the mass of the human body is made up of six elements: hydrogen (H), carbon (C), nitrogen (N), oxygen (O), calcium (Ca), and phosphorus (P). The next 0.75% is made up of the next five elements: potassium (K), sulfur (S), chlorine (Cl), sodium (Na), and magnesium (Mg). CHNOPS for short. Only 17 elements are known for certain to be necessary to human life, with one additional element (fluorine) thought to be helpful for tooth enamel strength. A few more trace elements may play some role in the health of mammals. Boron and silicon are notably necessary for plants but have uncertain roles in animals. The elements aluminium and silicon, although very common in the earth's crust, are conspicuously rare in the human body.
Group 12 element
Like in most other d-block groups, the abundance in Earth's crust of group 12 elements decreases with higher atomic number. Zinc is with 65 parts per million (ppm) the most abundant in the group while cadmium with 0.1 ppm and mercury with 0.08 ppm are orders of magnitude less abundant. Copernicium, as a synthetic element with a half-life of a few minutes, may only be present in the laboratories where it was produced.
Group 12 metals are chalcophiles, meaning the elements have low affinities for oxides and prefer to bond with sulfides. Chalcophiles formed as the crust solidified under the reducing conditions of the early Earth's atmosphere. The commercially most important minerals of group 12 elements are sulfide minerals. Sphalerite, which is a form of zinc sulfide, is the most heavily mined zinc-containing ore because its concentrate contains 60–62% zinc. No significant deposits of cadmium-containing ores are known. Greenockite (CdS), the only cadmium mineral of importance, is nearly always associated with sphalerite (ZnS). This association is caused by the geochemical similarity between zinc and cadmium which makes geological separation unlikely. As a consequence, cadmium is produced mainly as a byproduct from mining, smelting, and refining sulfidic ores of zinc, and, to a lesser degree, lead and copper. One place where metallic cadmium can be found is the Vilyuy River basin in Siberia. Although mercury is an extremely rare element in the Earth's crust, because it does not blend geochemically with those elements that constitute the majority of the crustal mass, mercury ores can be highly concentrated considering the element's abundance in ordinary rock. The richest mercury ores contain up to 2.5% mercury by mass, and even the leanest concentrated deposits are at least 0.1% mercury (12,000 times average crustal abundance). It is found either as a native metal (rare) or in cinnabar (HgS), corderoite, livingstonite and other minerals, with cinnabar being the most common ore.
Halogen
Halogens are highly reactive, and as such can be harmful or lethal to biological organisms in sufficient quantities. This high reactivity is due to the high electronegativity of the atoms due to their high effective nuclear charge. Because the halogens have seven valence electrons in their outermost energy level, they can gain an electron by reacting with atoms of other elements to satisfy the octet rule. Fluorine is one of the most reactive elements, attacking otherwise-inert materials such as glass, and forming compounds with the usually inert noble gases. It is a corrosive and highly toxic gas. The reactivity of fluorine is such that, if used or stored in laboratory glassware, it can react with glass in the presence of small amounts of water to form silicon tetrafluoride (SiF). Thus, fluorine must be handled with substances such as Teflon (which is itself an organofluorine compound), extremely dry glass, or metals such as copper or steel, which form a protective layer of fluoride on their surface.
II-VI semiconductor compound
II-VI semiconductor compounds are compounds composed of a metal from either group 2 or 12 of the periodic table (the alkaline earth metals and group 12 elements, formerly called groups IIA and IIB) and a nonmetal from group 16 (the chalcogens, formerly called group VI).
These semiconductors crystallize either in the zincblende lattice structure or the wurtzite crystal structure.
They generally exhibit large band gaps, making them popular for short wavelength applications in optoelectronics.
Chalcogen
Early attempts to separate oxygen from air were hampered by the fact that air was thought of as a single element up to the 17th and 18th centuries. Robert Hooke, Mikhail Lomonosov, Ole Borch, and Pierre Bayden all successfully created oxygen, but did not realize it at the time. Oxygen was discovered by Joseph Priestley in 1774 when he focused sunlight on a sample of mercuric oxide and collected the resulting gas. Carl Wilhelm Scheele had also created oxygen in 1771 by the same method, but Scheele did not publish his results until 1777.
Chalcogen
Alcohols, phenols and other similar compounds contain oxygen. However, in thiols, selenols and tellurols; sulfur, selenium, and tellurium replace oxygen. Thiols are better known than selenols or tellurols. Thiols are the most stable chalcogenols and tellurols are the least stable, being unstable in heat or light. Other organic chalcogen compounds include thioethers, selenoethers and telluroethers. Some of these, such as dimethyl sulfide, diethyl sulfide, and dipropyl sulfide are commercially available. Selenoethers are in the form of RSe or RSeR. Telluroethers such as dimethyl telluride are typically prepared in the same way as thioethers and selenoethers. Organic chalcogen compounds, especially organic sulfur compounds, have the tendency to smell unpleasant. Dimethyl telluride also smells unpleasant, and selenophenol is renowned for its "metaphysical stench". There are also thioketones, selenoketones, and telluroketones. Out of these, thioketones are the most well-studied with 80% of chalcogenoketones papers being about them. Selenoketones make up 16% of such papers and telluroketones make up 4% of them. Thioketones have well-studied non-linear electric and photophysic properties. Selenoketones are less stable than thioketones and telluroketones are less stable than selenoketones. Telluroketones have the highest level of polarity of chalcogenoketones.
Noble gas
In December 1998, scientists at the Joint Institute for Nuclear Research working in Dubna, Russia bombarded plutonium (Pu) with calcium (Ca) to produce a single atom of element 114, flerovium (Fl). Preliminary chemistry experiments have indicated this element may be the first superheavy element to show abnormal noble-gas-like properties, even though it is a member of group 14 on the periodic table. In October 2006, scientists from the Joint Institute for Nuclear Research and Lawrence Livermore National Laboratory successfully created synthetically oganesson (Og), the seventh element in group 18, by bombarding californium (Cf) with calcium (Ca).
The noble gases have weak interatomic force, and consequently have very low melting and boiling points. They are all monatomic gases under standard conditions, including the elements with larger atomic masses than many normally solid elements. Helium has several unique qualities when compared with other elements: its boiling and melting points are lower than those of any other known substance; it is the only element known to exhibit superfluidity; it is the only element that cannot be solidified by cooling under standard conditions—a pressure of must be applied at a temperature of to convert it to a solid. The noble gases up to xenon have multiple stable isotopes. Radon has no stable isotopes; its longest-lived isotope, Rn, has a half-life of 3.8 days and decays to form helium and polonium, which ultimately decays to lead. Melting and boiling points generally increase going down the group.
Chalcogen
Compounds with chalcogen-phosphorus bonds have been explored for more than 200 years. These compounds include unsophisticated phosphorus chalcogenides as well as large molecules with biological roles and phosphorus-chalcogen compounds with metal clusters. These compounds have numerous applications, including strike-anywhere matches and quantum dots. A total of 130,000 compounds with at least one phosphorus-sulfur bond, 6000 compounds with at least one phosphorus-selenium bond, and 350 compounds with at least one phosphorus-tellurium bond have been discovered. The decrease in the number of chalcogen-phosphorus compounds further down the periodic table is due to diminishing bond strength. Such compounds tend at least one phosphorus atom in the center, surrounded by four chalcogens and side chains. However, some phosphorus-chalcogen compounds also contain hydrogen (such as secondary phosphine chalcogenides) or nitrogen (such as dichalcogenoimidodiphosphates). Phosphorus selenides are typically harder to handle that phosphorus sulfides, and compounds in the form PTe have not been discovered. Chalcogens also bond with other pnictogens, such as arsenic, antimony, and bismuth. Heavier chalcogen pnictides tend to form ribbon-like polymers instead of individual molecules. Chemical formulas of these compounds include BiS and SbSe. Ternary chalcogen pnictides are also known. Examples of these include POSe and PSbS. salts containing chalcogens and pnictogens also exist. Almost all chalcogen pnictide salts are typically in the form of [PnE], where Pn is a pnictogen and E is a chalcogen. Tertiary phosphines can react with chalcogens to form compounds in the form of RPE, where E is a chalcogen. When E is sulfur, these compounds are relatively stable, but they are less so when E is selenium or tellurium. Similarly, secondary phosphines can react with chalcogens to form secondary phosphine chalcogenides. However, these compounds are in a state of equilibrium with chalcogenophosphinous acid. Secondary phosphine chalcogenides are weak acids. Binary compounds consisting of antimony or arsenic and a chalcogen. These compounds tend to be colorful and can be created by a reaction of the constituent elements at temperatures of .
Inorganic chemistry
These species feature elements from groups I, II, III, IV, V,VI, VII, 0 (excluding hydrogen) of the periodic table. Due to their often similar reactivity, the elements in group 3 (Sc, Y, and La) and group 12 (Zn, Cd, and Hg) are also generally included, and the lanthanides and actinides are sometimes included as well.
Halogen
The halogens () are a group in the periodic table consisting of five chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). The artificially created element 117 (tennessine, Ts) may also be a halogen. In the modern IUPAC nomenclature, this group is known as group 17. The symbol X is often used generically to refer to any halogen.
Chalcogen
Oxygen is the most electronegative element except for fluorine, and forms compounds with almost all of the chemical elements, including some of the noble gases. It commonly bonds with many metals and metalloids to form oxides, including iron oxide, titanium oxide, and silicon oxide. Oxygen's most common oxidation state is −2, and the oxidation state −1 is also relatively common. With hydrogen it forms water and hydrogen peroxide. Organic oxygen compounds are ubiquitous in organic chemistry.
Chalcogenide
For the purpose of classifying these materials, the chalcogenide is often viewed as a dianion, i.e., S, Se, Te, and Po. In fact, transition metal chalcogenides are highly covalent, not ionic, as indicated by their semiconducting properties.
Optical fiber
The chalcogens—the elements in group 16 of the periodic table—particularly sulfur (S), selenium (Se) and tellurium (Te)—react with more electropositive elements, such as silver, to form chalcogenides. These are extremely versatile compounds, in that they can be crystalline or amorphous, metallic or semiconducting, and conductors of ions or electrons. Glass containing chalcogenides can be used to make fibers for far infrared transmission.
Block (periodic table)
There is an approximate correspondence between this nomenclature of blocks, based on electronic configuration, and groupings of elements based on chemical properties. The s-block and p-block together are usually considered as the main-group elements, the d-block corresponds to the transition metals, and the f-block are the lanthanides and the actinides.
However, not everyone agrees on the exact membership of each set of elements, so that, for example the group 12 elements Zn, Cd and Hg are considered as main group by some scientists and transition metals by others, because they are chemically and physically more similar to the p-block elements than the other d-block elements. The group 3 elements are sometimes also considered main group elements due to their similarities to the s-block elements. Groups (columns) in the f-block (between groups 3 and 4) are not numbered.
Chalcogen
The first attempt at creating livermorium was from 1976 to 1977 at the LBNL, who bombarded curium-248 with calcium-48, but were not successful. After several failed attempts in 1977, 1998, and 1999 by research groups in Russia, Germany, and the US, livermorium was created successfully in 2000 at the Joint Institute for Nuclear Research by bombarding curium-248 atoms with calcium-48 atoms. The element was known as ununhexium until it was officially named livermorium in 2012.
Chalcogen
The chalcogens have varying crystal structures. Oxygen's crystal structure is monoclinic, sulfur's is orthorhombic, selenium and tellurium have the hexagonal crystal structure, while polonium has a cubic crystal structure.
Alkali metal
Cobaltocene, Co(CH), is a metallocene, the cobalt analogue of ferrocene. It is a dark purple solid. Cobaltocene has 19 valence electrons, one more than usually found in organotransition metal complexes, such as its very stable relative, ferrocene, in accordance with the 18-electron rule. This additional electron occupies an orbital that is antibonding with respect to the Co–C bonds. Consequently, many chemical reactions of Co(CH) are characterized by its tendency to lose this "extra" electron, yielding a very stable 18-electron cation known as cobaltocenium. Many cobaltocenium salts coprecipitate with caesium salts, and cobaltocenium hydroxide is a strong base that absorbs atmospheric carbon dioxide to form cobaltocenium carbonate. Like the alkali metals, cobaltocene is a strong reducing agent, and decamethylcobaltocene is stronger still due to the combined inductive effect of the ten methyl groups. Cobalt may be substituted by its heavier congener rhodium to give rhodocene, an even stronger reducing agent. Iridocene (involving iridium) would presumably be still more potent, but is not very well-studied due to its instability.
Gemstones in the Bible
Chalcedony, Apoc., xxi, 19, "chalkedon"; Vulg. "chalcedonius", the third foundation stone of the celestial Jerusalem. The view that the writing "chalkedon" is an error and that it should be "charkedon" (the carbuncle) is not without some reason. However, the other eleven stones correspond to a stone in the rational and this is the only exception. The ancients very often confounded the names of these two stones. Chalcedony is a siliceous stone. Its name is supposed to derive from Chalcedon, in Bithynia, where the ancients obtained the stone from. It is a species of agate and bears various names according to its colour. Chalcedony is usually made up of concentric circles of various colours and the most valuable of these stones are found in the East Indies. The gem is used for rings, seals and, in the East; drinking vessels.
Chalcogen bond
Due to a chalcogen's ability to function as an electron donor, many systems will balance between hydrogen bonding with the chalcogen as a donor or chalcogen bonding. This balance can be observed in a series of self-bonding intermolecular interactions between various substituted chalcogens. In cases with hard chalcogen atoms as acceptors, the balance favors H-bonding between chalcogen and methyl H. However, as the acceptor atoms move down the group, chalcogen-chalcogen bonding will be favored. It is hypothesized that electrostatic forces should only dominate in a chalcogen-chalcogen bond with lighter congeners, and instead that dispersion forces dominate in the cases of heavier congeners
Octahedral cluster
The premier example is of the class is MoCl. This dianion is available as a variety of salts by treating the polymer molybdenum(II) chloride with sources of chloride, even hydrochloric acid. A related example is WCl anion, which is obtained by extraction of tungsten(II) chloride.
A related class of octahedral clusters are of the type MXL where M is a metal usually of group 6 or group 7, X is a ligand and more specifically an inner ligand of the chalcohalide group such as chloride or sulfide and L is an "outer ligand." The metal atoms define the vertices of an octahedron. The overall point group symmetry is O. Each face of the octahedron is capped with a chalcohalide and eight such atoms are at the corners of a cube. For this reason this geometry is called a face capped octahedral cluster. Examples of this type of clusters are the ReSCl anion.
A well-studied class of solid-state compounds related to the chalcohalides are molybdenum clusters of the type AMoX with X sulfur or selenium and A an interstitial atom such as Pb. These materials, called Chevrel phases or Chevrel clusters, have been actively studied because they are type II superconductors with relatively high critical fields. Such materials are prepared by high temperature (1100 °C) reactions of the chalcogen and Mo metal. Structurally related, soluble analogues have been prepared, e.g., MoS(PEt).
Chalcogen
Oxygen is needed by almost all organisms for the purpose of generating ATP. It is also a key component of most other biological compounds, such as water, amino acids and DNA. Human blood contains a large amount of oxygen. Human bones contain 28% oxygen. Human tissue contains 16% oxygen. A typical 70-kilogram human contains 43 kilograms of oxygen, mostly in the form of water.
Chalcogel
Metal chalcogenide aerogels can be prepared from thiolysis or nanoparticle condensation contain crystalline nanoparticles in the structure. The chalcogels are made with the approach and belong to a different class of materials. The method used is based on the metathesis (or partner-switching) reaction, makes use of molecular chalcogenide anions and linking metal cations. These reactions give a random network, which does not have long-range periodic structure. By its nature this method gives the advantage of tuning the resulting material properties through appropriate selection of anions and cations. At the same time a judicious match of the anion and metal components is needed in order to force the building block and linker metals to engage in a controlled self-assembly process so a gel can be obtained. The key is to avoid rapid precipitation or a permanent solution where with no gelation is taking place. Based on this chemical approach chalcogels were first demonstrate using platinum linking ions, and thiogermanate or selenogermanate anions. The synthetic method can be extended to many thioanions including tetrathiomolybdate-based chalcogels. Different metal ions have been used as linkers Co, Ni, Pb, Cd, Bi, Cr.
Indium chalcogenides
There are a lot of compounds, the reason for this being that indium can be present as 
The compound InTe is a polytelluride containing the Te unit.
None of the indium chalcogenides can be described simply as ionic in nature, they all involve a degree of covalent bonding. However, in spite of this it is useful to formulate the compounds in ionic terms to get an insight into how the structures are built up. Compounds almost invariably have multiple polymorphs, that is they can crystallise in slightly different forms depending on either the method of production, or the substrate upon which they are deposited. Many of the compounds are made up of layers, and it is the different ways that the layers are stacked that is a cause of polymorphism. InS is an n-type semiconductor.
Group 11 element
Group 11, by modern IUPAC numbering, is a group of chemical elements in the periodic table, consisting of copper (Cu), silver (Ag), and gold (Au). Roentgenium (Rg) is also placed in this group in the periodic table, although no chemical experiments have yet been carried out to confirm that it behaves like the heavier homologue to gold. Group 11 is also known as the "coinage metals", due to their former usage. They were most likely the first three elements discovered. Copper, silver, and gold all occur naturally in elemental form.
Group 12 element
The elements in group 12 are usually considered to be d-block elements, but not transition elements as the d-shell is full. Some authors classify these elements as main-group elements because the valence electrons are in ns orbitals. Nevertheless, they share many characteristics with the neighboring group 11 elements on the periodic table, which are almost universally considered to be transition elements. For example, zinc shares many characteristics with the neighboring transition metal, copper. Zinc complexes merit inclusion in the Irving-Williams series as zinc forms many complexes with the same stoichiometry as complexes of copper(II), albeit with smaller stability constants. There is little similarity between cadmium and silver as compounds of silver(II) are rare and those that do exist are very strong oxidizing agents. Likewise the common oxidation state for gold is +3, which precludes there being much common chemistry between mercury and gold, though there are similarities between mercury(I) and gold(I) such as the formation of linear dicyano complexes, [M(CN)]. According to IUPAC's definition of transition metal as "an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell", zinc and cadmium are not transition metals, while mercury is. This is because only mercury is known to have a compound where its oxidation state is higher than +2, in mercury(IV) fluoride (though its existence is disputed, as later experiments trying to confirm its synthesis could not find evidence of HgF). However, this classification is based on one highly atypical compound seen at non-equilibrium conditions and is at odds to mercury's more typical chemistry, and Jensen has suggested that it would be better to regard mercury as not being a transition metal.
Hydrogen chalcogenide
One of the most well-known hydrogen chalcogenide ions is the hydroxide ion, and the related hydroxy functional group. The former is present in alkali metal, alkaline earth, and rare-earth hydroxides, formed by reacting the respective metal with water. The hydroxy group appears commonly in organic chemistry, such as within alcohols. The related bisulfide/sulfhydryl group appears in hydrosulfide salts and thiols, respectively.
Chalcogenide
Transition metal dichalcogenides typically adopt either cadmium diiodide or molybdenum disulfide structures. In the CdI motif, the metals exhibit octahedral structures. In the MoS motif, which is not observed for dihalides, the metals exhibit trigonal prismatic structures. The strong bonding between the metal and chalcogenide ligands, contrasts with the weak chalcogenide—chalcogenide bonding between the layers. Owing to these contrasting bond strengths, these materials engage in intercalation by alkali metals. The intercalation process is accompanied by charge transfer, reducing the M(IV) centers to M(III).
Chalcogel
Semiconducting metal chalcogenide aerogels, first demonstrated by Professor Stephanie Brock at Wayne State University, show great promise for use in chemical sensors, solar cells, and photoelectrolysis of water.
Group (periodic table)
In chemistry, a group (also known as a family) is a column of elements in the periodic table of the chemical elements. There are 18 numbered groups in the periodic table, and the f-block columns (between groups 3 and 4) are not numbered. The elements in a group have similar physical or chemical characteristics of the outermost electron shells of their atoms (i.e., the same core charge), as most chemical properties are dominated by the orbital location of the outermost electron.
There are three systems of group numbering. The modern numbering "group 1" to "group 18" is recommended by the International Union of Pure and Applied Chemistry (IUPAC). It replaces two older naming schemes that were mutually confusing. Also, groups may be identified by their topmost element or have a specific name. For example, group 16 is variously described as the "oxygen group" and as the chalcogens.
In history, several sets of group names have been used:
Chalcogen
Chalcogens form single bonds and double bonds with other carbon group elements than carbon, such as silicon, germanium, and tin. Such compounds typically form from a reaction of carbon group halides and chalcogenol salts or chalcogenol bases. Cyclic compounds with chalcogens, carbon group elements, and boron atoms exist, and occur from the reaction of boron dichalcogenates and carbon group metal halides. Compounds in the form of M-E, where M is silicon, germanium, or tin, and E is sulfur, selenium or tellurium have been discovered. These form when carbon group hydrides react or when heavier versions of carbenes react. Sulfur and tellurium can bond with organic compounds containing both silicon and phosphorus.
Indium chalcogenides
Some compounds that were reported and have found their way into text books have not been substantiated by later researchers. The list of compounds below shows compounds that have been reported, and those compounds that have not had their structure determined, or whose existence has not been confirmed by the latest structural investigations, are in italics.
Chalcogen
All of the chalcogens form hydrides. In some cases this occurs with chalcogens bonding with two hydrogen atoms. However tellurium hydride and polonium hydride are both volatile and highly labile. Also, oxygen can bond to hydrogen in a 1:1 ratio as in hydrogen peroxide, but this compound is unstable.
Europium
Europium forms stable compounds with all of the chalcogens, but the heavier chalcogens (S, Se, and Te) stabilize the lower oxidation state. Three oxides are known: europium(II) oxide (EuO), europium(III) oxide (EuO), and the mixed-valence oxide EuO, consisting of both Eu(II) and Eu(III).
Otherwise, the main chalcogenides are europium(II) sulfide (EuS), europium(II) selenide (EuSe) and europium(II) telluride (EuTe): all three of these are black solids. EuS is prepared by sulfiding the oxide at temperatures sufficiently high to decompose the EuO:
The main nitride is europium(III) nitride (EuN).
Term symbol
In the periodic table, because atoms of elements in a column usually have the same outer electron structure, and always have the same electron structure in the "s-block" and "p-block" elements (see block (periodic table)), all elements may share the same ground state term symbol for the column. Thus, hydrogen and the alkali metals are all S, the alkali earth metals are S, the boron column elements are P, the carbon column elements are P, the pnictogens are S, the chalcogens are P, the halogens are P, and the inert gases are "S", per the rule for full shells and subshells stated above.
Oganesson
Oganesson is a member of group 18, the zero-valence elements. The members of this group are usually inert to most common chemical reactions (for example, combustion) because the outer valence shell is completely filled with eight electrons. This produces a stable, minimum energy configuration in which the outer electrons are tightly bound. It is thought that similarly, oganesson has a closed outer valence shell in which its valence electrons are arranged in a 7s7p configuration.
Alternative periodic tables
Ronald L. Rich has proposed a periodic table where elements appear more than once when appropriate. He notes that hydrogen shares properties with group 1 elements based on valency, with group 17 elements because hydrogen is a non-metal but also with the carbon group based on similarities in chemical bonding to transition metals and a similar electronegativity. In this rendition of the periodic table carbon and silicon also appear in the same group as titanium and zirconium.
Chalcogen
Sulfur has been known since antiquity, and oxygen was recognized as an element in the 18th century. Selenium, tellurium and polonium were discovered in the 19th century, and livermorium in 2000. All of the chalcogens have six valence electrons, leaving them two electrons short of a full outer shell. Their most common oxidation states are −2, +2, +4, and +6. They have relatively low atomic radii, especially the lighter ones.
Boron group
The next group-13 elements, aluminium and gallium, form fewer stable hydrides, although both AlH and GaH exist. Indium, the next element in the group, is not known to form many hydrides, except in complex compounds such as the phosphine complex HInP(Cy). No stable compound of thallium and hydrogen has been synthesized in any laboratory.
Calclacite
Calclacite is a mineral and an organic compound. Its name references the components, which are calcium ions (Ca), chloride (Cl) and acetate CHCOO.
Chalcogenide glass
Some chalcogenide materials experience thermally driven amorphous-to-crystalline phase changes. This makes them useful for encoding binary information on thin films of chalcogenides and forms the basis of rewritable optical discs and non-volatile memory devices such as PRAM. Examples of such phase change materials are GeSbTe and AgInSbTe. In optical discs, the phase change layer is usually sandwiched between dielectric layers of ZnS-SiO, sometimes with a layer of a crystallization promoting film. Other less commonly used such materials are InSe, SbSe, SbTe, InSbSe, InSbTe, GeSbSe, GeSbTeSe and AgInSbSeTe.
Group 10 element
Group 10, numbered by current IUPAC style, is the group of chemical elements in the periodic table that consists of nickel (Ni), palladium (Pd), platinum (Pt), and perhaps also the chemically uncharacterized darmstadtium (Ds). All are d-block transition metals. All known isotopes of darmstadtium are radioactive with short half-lives, and are not known to occur in nature; only minute quantities have been synthesized in laboratories.
Industrial gas
The known chemical elements which are, or can be obtained from natural resources and which are gaseous are hydrogen, nitrogen, oxygen, fluorine, chlorine, plus the noble gases; and are collectively referred to by chemists as the "elemental gases". These elements are all primordial apart from the noble gas radon which is a trace radioisotope which occurs naturally since all isotopes are radiogenic nuclides from radioactive decay. (It is not known if any synthetic elements with atomic number above 108 are gases.)
The elements which are stable two atom homonuclear molecules at standard temperature and pressure (STP), are hydrogen (H), nitrogen (N) and oxygen (O), plus the halogens fluorine (F) and chlorine (Cl). The noble gases are all monatomic.
Main-group element
In chemistry and atomic physics, the main group is the group of elements whose lightest members are represented by helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, and fluorine as arranged in the periodic table of the elements. The main group includes the elements (except hydrogen, which is sometimes not included) in groups 1 and 2 (s-block), and groups 13 to 18 (p-block). The s-block elements are primarily characterised by one main oxidation state, and the p-block elements, when they have multiple oxidation states, often have common oxidation states separated by two units.
Chalcogenide
A chalcogenide is a chemical compound consisting of at least one chalcogen anion and at least one more electropositive element. Although all group 16 elements of the periodic table are defined as chalcogens, the term chalcogenide is more commonly reserved for sulfides, selenides, tellurides, and polonides, rather than oxides. Many metal ores exist as chalcogenides. Photoconductive chalcogenide glasses are used in xerography. Some pigments and catalysts are also based on chalcogenides. The metal dichalcogenide MoS is a common solid lubricant.
Hydrogen chalcogenide
The most important of these is hydrogen peroxide, HO, a pale blue, nearly colourless liquid that has a lower volatility than water and a higher density and viscosity. It is important chemically as it can be either oxidised or reduced in solutions of any pH, can readily form peroxometal complexes and peroxoacid complexes, as well as undergoing many proton acid/base reactions. In its less concentrated form hydrogen peroxide has some major household uses, such as a disinfectant or for bleaching hair; much more concentrated solutions are much more dangerous.