When was the periodic table developed?
History of chemistry
An important breakthrough in making sense of the list of known chemical elements (as well as in understanding the internal structure of atoms) was Dmitri Mendeleev's development of the first modern periodic table, or the periodic classification of the elements. Mendeleev, a Russian chemist, felt that there was some type of order to the elements and he spent more than thirteen years of his life collecting data and assembling the concept, initially with the idea of resolving some of the disorder in the field for his students. Mendeleev found that, when all the known chemical elements were arranged in order of increasing atomic weight, the resulting table displayed a recurring pattern, or periodicity, of properties within groups of elements. Mendeleev's law allowed him to build up a systematic periodic table of all the 66 elements then known based on atomic mass, which he published in "Principles of Chemistry" in 1869. His first Periodic Table was compiled on the basis of arranging the elements in ascending order of atomic weight and grouping them by similarity of properties.
History of the periodic table
In 1869, a few months later than Mendeleev, Meyer published a revised and expanded version of his 1864 table independently, which was similar to that published by Mendeleev (Meyer had been sent a copy of Mendeleev's table earlier; Mendeleev had sent it to many well-known chemists of his day) and a paper showing graphically the periodicity of the elements as a function of atomic weight.
Periodic trends
Discovery of Periodic Law constitutes one of the most singularly important events in the history of chemical science. Almost every chemist makes extensive and continued use of Periodic Law. Periodic Law also led to the development of the periodic table, which is widely used nowadays.
Periodic table
The popular periodic table layout, also known as the common or standard form (as shown at various other points in this article), is attributable to Horace Groves Deming. In 1923, Deming, an American chemist, published short (Mendeleev style) and medium (18-column) form periodic tables. Merck and Company prepared a handout form of Deming's 18-column medium table, in 1928, which was widely circulated in American schools. By the 1930s Deming's table was appearing in handbooks and encyclopaedias of chemistry. It was also distributed for many years by the Sargent-Welch Scientific Company.
Mathematical table
The first tables of trigonometric functions known to be made were by Hipparchus (c.190 – c.120 BCE) and Menelaus (c.70–140 CE), but both have been lost. Along with the surviving table of Ptolemy (c. 90 – c.168 CE), they were all tables of chords and not of half-chords, i.e. the sine function. The table produced by the Indian mathematician Āryabhaṭa is considered the first sine table ever constructed. 
Āryabhaṭa's table remained the standard sine table of ancient India. There were continuous attempts to improve the accuracy of this table, culminating in the discovery of the power series expansions of the sine and cosine functions by Madhava of Sangamagrama (c.1350 – c.1425), and the tabulation of a sine table by Madhava with values accurate to seven or eight decimal places.
List of important publications in chemistry
Importance: Topic Creator, Breakthrough, Influence. The book was one of the first to describe a modern atomic theory, a theory that lies at the basis of modern chemistry. It is the first to introduce a table of atomic and molecular weights. Surprisingly, given the period in which the book was written, of the five properties of atoms that Dalton listed, only two have been shown to be incorrect.Description and Importance: In this paper the periodic table was introduced.
Notice that the table in the above link is the original one. Since then the table structure was slightly changed and new elements were added to it.Description: Contains synthetic models selected by world-renowned experts, with full experimental procedures and background information. Considers methods from journals, books, and patent literature from the early 19th century up to the present day and presents important synthetic methods for all classes of compounds. Critically evaluates the preparative applicability and significance of the synthetic methods.
Babylonia
Tablets dating back to the Old Babylonian period document the application of mathematics to the variation in the length of daylight over a solar year. Centuries of Babylonian observations of celestial phenomena are recorded in the series of cuneiform script tablets known as the 'Enūma Anu Enlil'. The oldest significant astronomical text that we possess is Tablet 63 of 'Enūma Anu Enlil', the Venus tablet of Ammi-Saduqa, which lists the first and last visible risings of Venus over a period of about 21 years and is the earliest evidence that the phenomena of a planet were recognized as periodic. The oldest rectangular astrolabe dates back to Babylonia c. 1100 BC. The MUL.APIN, contains catalogues of stars and constellations as well as schemes for predicting heliacal risings and the settings of the planets, lengths of daylight measured by a water clock, gnomon, shadows, and intercalations. The Babylonian GU text arranges stars in 'strings' that lie along declination circles and thus measure right-ascensions or time-intervals, and also employs the stars of the zenith, which are also separated by given right-ascensional differences.
History of the periodic table
During his Manhattan Project research in 1943, Glenn T. Seaborg experienced unexpected difficulties in isolating the elements americium and curium. Seaborg wondered if these elements belonged to a different series, which would explain why their chemical properties were different from what was expected. In 1945, against the advice of colleagues, he proposed a significant change to Mendeleev's table: the actinide series.
Hugo Stintzing
In 1916 he proposed a model for the periodic table, organized as a cone-like rotational body. His paper, "Eine neue Anordnung des periodischen Systems der Elemente" (A new arrangement of the periodic system of the elements) was published in "Zeitschrift für Physikalische Chemie". His representation of the elements is one of several early helix-based displays.
Alternative periodic tables
Alternative periodic tables are tabulations of chemical elements differing significantly in their organization from the traditional depiction of the periodic system. Several have been devised, often purely for didactic reasons, as not all correlations between the chemical elements are effectively captured by the standard periodic table.
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.
Periodic table (detailed cells)
The periodic table is a tabular method of displaying the chemical elements. It can show much information, after name, symbol and atomic number. Also, for each element mean atomic mass value for the natural isotopic composition of each element can be noted. 
The two layout forms originate from two graphic forms of presentation of the same periodic table. Historically, when the f-block was identified it was drawn below the existing table, with markings for its in-table location (this page uses dots or asterisks). Also, a common presentation is to put all 15 lanthanide and actinide columns below, while the f-block only has 14 columns. One lanthanide and actinide each are d-block elements, belonging to group 3 with scandium and yttrium, though whether these are the first of each series (lanthanum and actinium) or the last (lutetium and lawrencium) has been disputed. The tables below show lanthanum and actinium as group 3 elements, as this is the more common form in the literature.
History of the periodic table
The history of the periodic table is also a history of the discovery of the chemical elements. The first person in history to discover a new element was Hennig Brand, a bankrupt German merchant. Brand tried to discover the Philosopher's Stone — a mythical object that was supposed to turn inexpensive base metals into gold. In 1669 (or later), his experiments with distilled human urine resulted in the production of a glowing white substance, which he called "cold fire" ("kaltes Feuer"). He kept his discovery secret until 1680, when Robert Boyle rediscovered phosphorus and published his findings. The discovery of phosphorus helped to raise the question of what it meant for a substance to be an element.
Tabula (game)
According to the "Etymologiae" by Isidore of Seville, tabula was first invented by a Greek soldier of the Trojan War named Alea. The earliest description of "τάβλι" (tavli) is in an epigram of Byzantine emperor Zeno (r. 474–475; 476–491), given by Agathias of Myrine (6th century AD), who describes a game in which Zeno goes from a strong position to a very weak one after an unfortunate dice roll. The rules of Tabula were reconstructed in the 19th century by Becq de Fouquières based upon this epigram. The game was played on a board nearly identical to a modern backgammon board with 24 points, 12 on each side. Two players had 15 pieces each, and moved them in opposing directions around the board, according to the roll of three dice. A piece resting alone in a space on the board was vulnerable to being hit. Hitting a blot, reentering a piece from the bar, and bearing off, all had the same rules as today. The only differences with modern backgammon were the use of an extra die (three rather than two) and the starting of all pieces off the board (with them entering in the same way that pieces on the bar enter in modern backgammon).
Edgar James Banks
Banks is credited with the discovery of the Plimpton 322 tablet in Southern Iraq. It is believed to be the world’s oldest trigonometric table, predating Hipparchus by around 1000 years and, using base 60, also the most accurate trigonometric table, avoiding inexact numbers. It thus displayed knowledge of the Pythagorean theorem long before the birth of Pythagoras himself. The ancient cuneiform tablet was sold to the New York publisher George Arthur Plimpton, reportedly for $10. It was housed in Plimpton's private collection before being donated to Columbia University upon Plimpton's death. The artifact, now famously known as Plimpton 322 (denoting that it is the 322nd item in the catalog), has provided great insight into the Babylonian era mathematics.
Chemical element
Although earlier precursors to this presentation exist, its invention is generally credited to the Russian chemist Dmitri Mendeleev in 1869, who intended the table to illustrate recurring trends in the properties of the elements. The layout of the table has been refined and extended over time as new elements have been discovered and new theoretical models have been developed to explain chemical behavior.
John Newlands (chemist)
After Dmitri Mendeleev and Lothar Meyer received the Davy Medal from the Royal Society for their later 'discovery' of the periodic table, Newlands fought for recognition of his earlier work and eventually received the Davy Medal in 1887.
Dmitri Mendeleev
Mendeleev published his periodic table of all known elements and predicted several new elements to complete the table in a Russian-language journal. Only a few months after, Meyer published a virtually identical table in a German-language journal. Mendeleev has the distinction of accurately predicting the qualities of what he called ekasilicon, ekaaluminium and ekaboron (germanium, gallium and scandium, respectively).
Gdańsk University of Technology
The periodic table originally painted in 1904 and discovered during the renovation of the Chemical Auditorium reflects the knowledge of chemistry in the early 20th century.
History of the periodic table
In 1817, Johann Wolfgang Döbereiner, a chemist, began to formulate one of the earliest attempts to classify the elements. In 1829, he found that he could form some of the elements into groups of three, with the members of each group having related properties. He termed these groups "triads".
Periodic table of shapes
The periodic table of mathematical shapes is popular name given to a project to classify Fano varieties. The project was thought up by Professor Alessio Corti, from the Department of Mathematics at Imperial College London. It aims to categorise all three-, four- and five-dimensional shapes into a single table, analogous to the periodic table of chemical elements. It is meant to hold the equations that describe each shape and, through this, mathematicians and other scientists expect to develop a better understanding of the shapes’ geometric properties and relations.
Periodic table
The modern periodic table is sometimes expanded into its long or 32-column form by reinstating the footnoted f-block elements into their natural position between the s- and d-blocks. Unlike the 18-column form this arrangement results in "no interruptions in the sequence of increasing atomic numbers". The relationship of the f-block to the other blocks of the periodic table also becomes easier to see. Jensen advocates a form of table with 32 columns on the grounds that the lanthanides and actinides are otherwise relegated in the minds of students as dull, unimportant elements that can be quarantined and ignored. Despite these advantages the 32-column form is generally avoided by editors on account of its undue rectangular ratio (compared to a book page ratio), and the familiarity of chemists with the modern form (as introduced by Seaborg).
Plane table
The earliest mention of a plane table dates to 1551 in Abel Foullon's ""Usage et description de l'holomètre"", published in Paris. However, since Foullon's description was of a complete, fully developed instrument, it must have been invented earlier.
Theodore Gray
After amassing thousands of samples of elements, he assembled them into a four-legged physical table representing the periodic table. The finished table was awarded the 2011 ACS Grady Stack Award for Interpreting Chemistry for the Public, as well as the 2002 Ig Nobel Award for Chemistry. Gray's love of the periodic table would lead him to team up with photographer Nick Mann in creating "The Elements: A Visual Exploration of Every Known Atom in the Universe" and "Elements Vault."
Food composition data
Food composition tables in the format known today were published towards the end of the 19th century although, some tables on the chemical composition of mineral waters were assembled by Morveau as early as 1780. In 1896, tables from the USA were published, incorporating nearly 2600 analyses of a wide range of foods including the main food groups, as well as some processed foods. Values for foods were presented as ‘refuse’, water, protein, fats, carbohydrates, ash, and ‘fuel value’.
William Odling
In the 1860s Odling, like many chemists, was working towards classifying the elements, an effort that would eventually lead to the periodic table of elements. He was intrigued by atomic weights and the periodic occurrence of chemical properties. William Odling and Lothar Meyer drew up tables similar, but with improvements on, Dmitri Mendeleev's original table. Odling drew up a table of elements using repeating units of seven elements, which bears a striking resemblance to Mendeleev's first table. The groups are horizontal, the elements are in order of increasing atomic weight and there are vacant slots for undiscovered ones. In addition, Odling overcame the tellurium-iodine problem and he even managed to get thallium, lead, mercury and platinum in the right groups - something that Mendeleev failed to do at his first attempt.
Rudolphine Tables
In 1551, following the publication of "De revolutionibus orbium coelestium" by Nicholas Copernicus, Erasmus Reinhold produced the "Prutenic Tables" based on a heliocentric model of the Solar System, but these were no more accurate than the earlier tables.
History of astronomy
The first evidence of recognition that astronomical phenomena are periodic and of the application of mathematics to their prediction is Babylonian. Tablets dating back to the Old Babylonian period document the application of mathematics to the variation in the length of daylight over a solar year. Centuries of Babylonian observations of celestial phenomena are recorded in the series of cuneiform tablets known as the "Enūma Anu Enlil". The oldest significant astronomical text that we possess is Tablet 63 of the "Enūma Anu Enlil", the Venus tablet of Ammi-saduqa, which lists the first and last visible risings of Venus over a period of about 21 years and is the earliest evidence that the phenomena of a planet were recognized as periodic. The MUL.APIN, contains catalogues of stars and constellations as well as schemes for predicting heliacal risings and the settings of the planets, lengths of daylight measured by a water clock, gnomon, shadows, and intercalations. The Babylonian GU text arranges stars in 'strings' that lie along declination circles and thus measure right-ascensions or time-intervals, and also employs the stars of the zenith, which are also separated by given right-ascensional differences.
Alternative periodic tables
H. G. Deming used the so-called long periodic table (18 columns) in his textbook "General Chemistry", which appeared in the USA for the first time in 1923 (Wiley), and was the first to designate the first two and the last five main groups with the notation "A", and the intervening transition groups with the notation "B".
Desk
The basic desk forms were developed mostly in the 17th and 18th centuries. The modern ergonomic desk is a refinement of the mechanically complex drawing table or drafting table from the end of the 18th century.
Periodic table
In 1862, Alexandre-Emile Béguyer de Chancourtois, a French geologist, published an early form of periodic table, which he called the telluric helix or screw. He was the first person to notice the periodicity of the elements. With the elements arranged in a spiral on a cylinder by order of increasing atomic weight, de Chancourtois showed that elements with similar properties seemed to occur at regular intervals. His chart included some ions and compounds in addition to elements. His paper also used geological rather than chemical terms and did not include a diagram; as a result, it received little attention until the work of Dmitri Mendeleev.
In 1864, Julius Lothar Meyer, a German chemist, published a table with 28 elements. Realizing that an arrangement according to atomic weight did not exactly fit the observed periodicity in chemical properties he gave valency priority over minor differences in atomic weight. A missing element between Si and Sn was predicted with atomic weight 73 and valency 4. Concurrently, English chemist William Odling published an arrangement of 57 elements, ordered on the basis of their atomic weights. With some irregularities and gaps, he noticed what appeared to be a periodicity of atomic weights among the elements and that this accorded with "their usually received groupings". Odling alluded to the idea of a periodic law but did not pursue it. He subsequently proposed (in 1870) a valence-based classification of the elements.
History of chemistry
Mendeleev had such faith in the validity of the periodic law that he proposed changes to the generally accepted values for the atomic weight of a few elements and, in his version of the periodic table of 1871, predicted the locations within the table of unknown elements together with their properties. He even predicted the likely properties of three yet-to-be-discovered elements, which he called ekaboron (Eb), ekaaluminium (Ea), and ekasilicon (Es), which proved to be good predictors of the properties of scandium, gallium, and germanium, respectively, which each fill the spot in the periodic table assigned by Mendeleev.
History of chemistry
At first the periodic system did not raise interest among chemists. However, with the discovery of the predicted elements, notably gallium in 1875, scandium in 1879, and germanium in 1886, it began to win wide acceptance. The subsequent proof of many of his predictions within his lifetime brought fame to Mendeleev as the founder of the periodic law. This organization surpassed earlier attempts at classification by Alexandre-Émile Béguyer de Chancourtois, who published the telluric helix, an early, three-dimensional version of the periodic table of the elements in 1862, John Newlands, who proposed the law of octaves (a precursor to the periodic law) in 1864, and Lothar Meyer, who developed an early version of the periodic table with 28 elements organized by valence in 1864. Mendeleev's table did not include any of the noble gases, however, which had not yet been discovered. Gradually the periodic law and table became the framework for a great part of chemical theory. By the time Mendeleev died in 1907, he enjoyed international recognition and had received distinctions and awards from many countries.
History of the periodic table
In 1864, the English chemist John Newlands classified the sixty-two known elements into eight groups, based on their physical properties.
Dmitri Mendeleev
After becoming a teacher in 1867, Mendeleev wrote the definitive textbook of his time: "Principles of Chemistry" (two volumes, 1868–1870). It was written as he was preparing a textbook for his course. This is when he made his most important discovery. As he attempted to classify the elements according to their chemical properties, he noticed patterns that led him to postulate his periodic table; he claimed to have envisioned the complete arrangement of the elements in a dream:
Boron group
Gallium minerals were not known before August 1875, when the element itself was discovered. It was one of the elements that the inventor of the periodic table, Dmitri Mendeleev, had predicted to exist six years earlier. While examining the spectroscopic lines in zinc blende the French chemist Paul Emile Lecoq de Boisbaudran found indications of a new element in the ore. In just three months he was able to produce a sample, which he purified by dissolving it in a potassium hydroxide (KOH) solution and sending an electric current through it. The next month he presented his findings to the French Academy of Sciences, naming the new element after the Greek name for Gaul, modern France.
Extended periodic table (detailed cells)
The current standard table contains 7 "periods", culminating in oganesson, which has atomic number 118. The layout of the table has been refined and extended over time, as new elements have been discovered, and new theoretical models have been developed to explain chemical behavior. If further elements with higher atomic numbers than this are discovered, they will be placed in additional periods, laid out (as with the existing periods) to illustrate periodically recurring trends in the properties of the elements concerned. Any additional periods are expected to contain a larger number of elements than the seventh period, as they are calculated to have an additional so-called g-block, containing 18 elements with partially filled "g-orbitals" in each period. An eight-period table containing this block was suggested by Glenn T. Seaborg in 1969.
Periodic table
English chemist John Newlands produced a series of papers from 1863 to 1866 noting that when the elements were listed in order of increasing atomic weight, similar physical and chemical properties recurred at intervals of eight; he likened such periodicity to the octaves of music. This so termed Law of Octaves was ridiculed by Newlands' contemporaries, and the Chemical Society refused to publish his work. Newlands was nonetheless able to draft a table of the elements and used it to predict the existence of missing elements, such as germanium. The Chemical Society only acknowledged the significance of his discoveries five years after they credited Mendeleev.
Periodic table (disambiguation)
The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number, electron configurations, and recurring chemical properties, whose adopted structure shows periodic trends.
Annuity (European)
The first author who fully developed the powers of the table was John Nicholas Tetens, a native of Schleswig, who in 1785, while professor of philosophy and mathematics at Kiel, published in the German language an "Introduction to the Calculation of Life Annuities and Assurances". This work appears to have been quite unknown in England until F. Hendriks gave, in the first number of the "Assurance Magazine", pp. 1–20 (Sept. 1850), an account of it, with a translation of the passages describing the construction and use of the commutation table, and a sketch of the author's life and writings, to which we refer the reader who desires fuller information. It may be mentioned here that Tetens also gave only a specimen table, apparently not imagining that persons using his work would find it extremely useful to have a series of commutation tables, calculated and printed ready for use.
Periodic table
In 1867, Gustavus Hinrichs, a Danish born academic chemist based in America, published a spiral periodic system based on atomic spectra and weights, and chemical similarities. His work was regarded as idiosyncratic, ostentatious and labyrinthine and this may have militated against its recognition and acceptance.
Periodic table
The recognition and acceptance afforded to Mendeleev's table came from two decisions he made. The first was to leave gaps in the table when it seemed that the corresponding element had not yet been discovered. Mendeleev was not the first chemist to do so, but he was the first to be recognized as using the trends in his periodic table to predict the properties of those missing elements, such as gallium and germanium. The second decision was to occasionally ignore the order suggested by the atomic weights and switch adjacent elements, such as tellurium and iodine, to better classify them into chemical families.
History of the periodic table
In 1661, Boyle defined an element as "those primitive and simple Bodies of which the mixt ones are said to be composed, and into which they are ultimately resolved."
Julius Lothar Meyer
Julius Lothar Meyer (19 August 1830 – 11 April 1895) was a German chemist. He was one of the pioneers in developing the first periodic table of chemical elements. Both Mendeleev and Meyer worked with Robert Bunsen. He never used his first given name, and was known throughout his life simply as Lothar Meyer.
Alternative periodic tables
In Theodor Benfey's periodic table (1964), the elements form a two-dimensional spiral, starting from hydrogen, and folding their way around two peninsulars, the transition metals, and lanthanides and actinides. A superactinide island is already slotted in. The Chemical Galaxy (2004) is organized in a similar way.
2019
2019 has been designated as International Year of the Periodic Table of Chemical Elements by the United Nations General Assembly given that it coincides with the 150th anniversary of its creation by Dmitri Mendeleev in 1869.
Primo Levi
He wrote two other highly praised memoirs, ("Moments of Reprieve", 1978) and ("The Periodic Table", 1975). "Moments of Reprieve" deals with characters he observed during imprisonment. "The Periodic Table" is a collection of short pieces, based in episodes from his life but including two short stories that he wrote before his time in Auschwitz. Each story was related in some way to one of the chemical elements. At London's Royal Institution on 19 October 2006, "The Periodic Table" was voted onto the shortlist for the best science book ever written.
Multiplication table
The oldest known multiplication tables were used by the Babylonians about 4000 years ago. However, they used a base of 60. The oldest known tables using a base of 10 are the Chinese decimal multiplication table on bamboo strips dating to about 305 BC, during China's Warring States period.
The multiplication table is sometimes attributed to the ancient Greek mathematician Pythagoras (570–495 BC). It is also called the Table of Pythagoras in many languages (for example French, Italian and Russian), sometimes in English. The Greco-Roman mathematician Nichomachus (60–120 AD), a follower of Neopythagoreanism, included a multiplication table in his "Introduction to Arithmetic", whereas the oldest surviving Greek multiplication table is on a wax tablet dated to the 1st century AD and currently housed in the British Museum.
Annuity (European)
"Commutation tables", aptly so named in 1840 by Augustus De Morgan (see his paper "On the Calculation of Single Life Contingencies," "Assurance Magazine", xii. 328), show the proportion in which a benefit due at one age ought to be changed, so as to retain the same value and be due at another age. The earliest known specimen of a commutation table is contained in William Dale's "Introduction to the Study of the Doctrine of Annuities", published in 1772. A full account of this work is given by F. Hendriks in the second number of the "Assurance Magazine", pp. 15–17. William Morgan's "Treatise on Assurances", 1779, also contains a commutation table. Morgan gives the table as furnishing a convenient means of checking the correctness of the values of annuities found by the ordinary process. It may be assumed that he was aware that the table might be used for the direct calculation of annuities; but he appears to have been ignorant of its other uses.
Lookup table
In ancient (499 AD) India, Aryabhata created one of the first sine tables, which he encoded in a Sanskrit-letter-based number system. In 493 AD, Victorius of Aquitaine wrote a 98-column multiplication table which gave (in Roman numerals) the product of every number from 2 to 50 times and the rows were "a list of numbers starting with one thousand, descending by hundreds to one hundred, then descending by tens to ten, then by ones to one, and then the fractions down to 1/144" Modern school children are often taught to memorize "times tables" to avoid calculations of the most commonly used numbers (up to 9 x 9 or 12 x 12).
Russian culture
Nikolai Lobachevsky, a "Copernicus of Geometry", developed the non-Euclidean geometry. Dmitry Mendeleev invented the Periodic table, the main framework of the modern chemistry. Nikolay Benardos introduced the arc welding, further developed by Nikolay Slavyanov, Konstantin Khrenov and other Russian engineers. Gleb Kotelnikov invented the knapsack parachute, while Evgeniy Chertovsky introduced the pressure suit. Pavel Yablochkov and Alexander Lodygin were great pioneers of electrical engineering and inventors of early electric lamps.
History of the periodic table
His book, Die modernen Theorien der Chemie, which he began writing in Breslau in 1862 and which was published two years later, contained an early version of the periodic table containing 28 elements, classified elements into six families by their valence—for the first time, elements had been grouped according to their valence. Works on organizing the elements by atomic weight, until then had been stymied by inaccurate measurements of the atomic weights.
Dionysius Exiguus' Easter table
Dionysius Exiguus's Easter table was constructed in the year 525 by Dionysius Exiguus for the years 532–626. He obtained it from an Easter table attributed to Patriarch Cyril of Alexandria for the years 437–531. The latter was constructed around the year 440 by means of extrapolation from an Alexandrian Easter table constructed around the year 390 by Patriarch Theophilus of Alexandria. The great historical importance of Dionysius' Easter table is twofold:
Rudolphine Tables
The Rudolphine Tables () consist of a star catalogue and planetary tables published by Johannes Kepler in 1627, using some observational data collected by Tycho Brahe (1546–1601). The tables are named as "Rudolphine" in memory of Rudolf II, Holy Roman Emperor.
History of Western civilization
The 1859 publication of "On the Origin of Species", by the English naturalist Charles Darwin, provided an alternative hypothesis for the development, diversification, and design of human life to the traditional poetic scriptural explanation known as Creationism. According to Darwin, only the organisms most able to adapt to their environment survived while others became extinct. Adaptations resulted in changes in certain populations of organisms which could eventually cause the creation of new species. Modern genetics started with Gregor Johann Mendel, a German-Czech Augustinian monk who studied the nature of inheritance in plants. In his 1865 paper "Versuche über Pflanzenhybriden" ("Experiments on Plant Hybridization"), Mendel traced the inheritance patterns of certain traits in pea plants and described them mathematically. Louis Pasteur and Joseph Lister made discoveries about bacteria and its effects on humans. Geologists at the time made discoveries indicating the world was far older than most believed it to be. Early batteries were invented and a telegraph system was also invented, allowing global communication. In 1869 Russian chemist Dmitri Mendeleev published his Periodic table. The success of Mendeleev's table came from two decisions he made: The first was to leave gaps in the table when it seemed that the corresponding element had not yet been discovered. The second decision was to occasionally ignore the order suggested by the atomic weights and switch adjacent elements, such as cobalt and nickel, to better classify them into chemical families. At the end of the 19th century, a number of discoveries were made in physics which paved the way for the development of modern physics – including Maria Skłodowska-Curie's work on radioactivity.
Jacques de Billy
In the field of astronomy, he published several astronomical tables. First published in Dijon by Pierre Palliot in 1656, Billy's tables of eclipses is called "Tabulae Lodoicaeae seu universa eclipseon doctrina tabulis, praeceptis ac demonstrationibus explicata. Adiectus est calculus, aliquot eclipseon solis & lunae, quae proxime per totam Europam videbuntur". The tables were calculated for the years 1656 to 1693. This work also contains solar and lunar tables based on the Paris meridian. It also includes a detailed examination of problems involved in astronomical calculations.
Periodic table
Since the properties of an element are mostly determined by its electron configuration, the properties of the elements likewise show recurring patterns or periodic behaviour, some examples of which are shown in the diagrams below for atomic radii, ionization energy and electron affinity. It is this periodicity of properties, manifestations of which were noticed well before the underlying theory was developed, that led to the establishment of the periodic law (the properties of the elements recur at varying intervals) and the formulation of the first periodic tables.
Periodic table
Although minute quantities of some transuranic elements occur naturally, they were all first discovered in laboratories. Their production has expanded the periodic table significantly, the first of these being neptunium, synthesized in 1939. Because many of the transuranic elements are highly unstable and decay quickly, they are challenging to detect and characterize when produced. There have been controversies concerning the acceptance of competing discovery claims for some elements, requiring independent review to determine which party has priority, and hence naming rights. In 2010, a joint Russia–US collaboration at Dubna, Moscow Oblast, Russia, claimed to have synthesized six atoms of tennessine (element 117), making it the most recently claimed discovery. It, along with nihonium (element 113), moscovium (element 115), and oganesson (element 118), are the four most recently named elements, whose names all became official on 28 November 2016.
Extended periodic table
An extended periodic table theorizes about chemical elements beyond those currently known in the periodic table and proven up through oganesson, which completes the seventh period (row) in the periodic table at atomic number ("Z") 118.
C. H. D. Buys Ballot
Buys Ballot devised a tabular method for investigating periodicity in time series. In 1847 he used the table now named after him to determine the period of the sun's rotation from daily observations of temperature in the Netherlands from 1729 to 1846.
Āryabhaṭa's sine table
Āryabhaṭa's table was the first sine table ever constructed in the history of mathematics. The now lost tables of Hipparchus (c.190 BC – c.120 BC) and Menelaus (c.70–140 CE) and those of Ptolemy (c.AD 90 – c.168) were all tables of chords and not of half-chords.
Āryabhaṭa's table remained as the standard sine table of ancient India. There were continuous attempts to improve the accuracy of this table. These endeavors culminated in the eventual discovery of the power series expansions of the sine and cosine functions by Madhava of Sangamagrama (c.1350 – c.1425), the founder of the Kerala school of astronomy and mathematics, and the tabulation of a sine table by Madhava with values accurate to seven or eight decimal places.
Ptolemy's table of chords
The table of chords, created by the astronomer, geometer, and geographer Ptolemy in Egypt during the 2nd century AD, is a trigonometric table in Book I, chapter 11 of Ptolemy's "Almagest", a treatise on mathematical astronomy. It is essentially equivalent to a table of values of the sine function. It was the earliest trigonometric table extensive enough for many practical purposes, including those of astronomy (an earlier table of chords by Hipparchus gave chords only for arcs that were multiples of ). Centuries passed before more extensive trigonometric tables were created. One such table is the "Canon Sinuum" created at the end of the 16th century.
Group 3 element
In 1869, Russian chemist Dmitri Mendeleev published his periodic table, which had empty spaces for elements directly above and under yttrium. Mendeleev made several predictions on the upper neighbor of yttrium, which he called "eka-boron". Swedish chemist Lars Fredrik Nilson and his team discovered the missing element in the minerals euxenite and gadolinite and prepared 2 grams of scandium(III) oxide of high purity. He named it scandium, from the Latin "Scandia" meaning "Scandinavia". Chemical experiments on the element proved that Mendeleev's suggestions were correct; along with discovery and characterization of gallium and germanium this proved the correctness of the whole periodic table and periodic law. Nilson was apparently unaware of Mendeleev's prediction, but Per Teodor Cleve recognized the correspondence and notified Mendeleev. Metallic scandium was produced for the first time in 1937 by electrolysis of a eutectic mixture, at 700–800 °C, of potassium, lithium, and scandium chlorides.
Surveying
Abel Foullon described a plane table in 1551, but it is thought that the instrument was in use earlier as his description is of a developed instrument.
Numerology
The discovery of atomic triads, an early attempt to sort the elements into some logical order by their physical properties, was once considered a form of numerology, and yet ultimately led to the construction of the periodic table. Here the atomic weight of the lightest element and the heaviest are summed, and averaged, and the average is found to be very close to that of the intermediate weight element. This didn't work with every triplet in the same group, but worked often enough to allow later workers to create generalizations.
History of the periodic table
He contributed the word 'periodic' in chemistry.
Edward G. Mazurs
A revised "centenary" edition covering a full 100 years of periodic tables was republished under the title "Graphic Representations of the Periodic System During One Hundred Years " in 1974. Mazurs provided a comprehensive analysis and classification of periodic tables, listing and classifying over 700 periodic tables. He recommended Charles Janet's left-step system and suggested that it could be expanded into three dimensions.
Period (periodic table)
A period in the periodic table is a horizontal row. All elements in a row have the same number of electron shells. Each next element in a period has one more proton and is less metallic than its predecessor. Arranged this way, groups of elements in the same column have similar chemical and physical properties, reflecting the periodic law. For example, the alkali metals lie in the first column (group 1) and share similar properties, such as high reactivity and the tendency to lose one electron to arrive at a noble-gas electronic configuration. As of 2016, a total of 118 elements have been discovered and confirmed.
Modern quantum mechanics explains these periodic trends in properties in terms of electron shells. As atomic number increases, shells fill with electrons in approximately the order shown at right. The filling of each shell corresponds to a row in the table.
Scandium
Dmitri Mendeleev, who is referred to as the father of the periodic table, predicted the existence of an element "ekaboron", with an atomic mass between 40 and 48 in 1869. Lars Fredrik Nilson and his team detected this element in the minerals euxenite and gadolinite in 1879. Nilson prepared 2 grams of scandium oxide of high purity. He named the element scandium, from the Latin "Scandia" meaning "Scandinavia". Nilson was apparently unaware of Mendeleev's prediction, but Per Teodor Cleve recognized the correspondence and notified Mendeleev.
Periodic table
The many different forms of periodic table have prompted the question of whether there is an optimal or definitive form of periodic table. The answer to this question is thought to depend on whether the chemical periodicity seen to occur among the elements has an underlying truth, effectively hard-wired into the universe, or if any such periodicity is instead the product of subjective human interpretation, contingent upon the circumstances, beliefs and predilections of human observers. An objective basis for chemical periodicity would settle the questions about the location of hydrogen and helium, and the composition of group 3. Such an underlying truth, if it exists, is thought to have not yet been discovered. In its absence, the many different forms of periodic table can be regarded as variations on the theme of chemical periodicity, each of which explores and emphasizes different aspects, properties, perspectives and relationships of and among the elements.
Dispilio Tablet
The Dispilio tablet is a wooden tablet bearing inscribed markings, unearthed during George Hourmouziadis's excavations of Dispilio in Greece, and carbon 14-dated to 5202 (± 123) BC. It was discovered in 1993 in a Neolithic lakeshore settlement that occupied an artificial island near the modern village of Dispilio on Lake Kastoria in Kastoria, Western Macedonia, Greece.
The Periodic Table of Science Fiction
The Periodic Table of Science Fiction is a collection of 118 very short stories by science fiction author Michael Swanwick. Each story is named after an element in the periodic table, including the then-undiscovered element 117.
Prutenic Tables
The Prutenic Tables ( from "Prutenia" meaning "Prussia", ), were an ephemeris (astronomical tables) by the astronomer Erasmus Reinhold published in 1551. They are sometimes called the Prussian Tables after Albert I, Duke of Prussia, who supported Reinhold and financed the printing. Reinhold calculated this new set of astronomical tables based on Nicolaus Copernicus' "De revolutionibus orbium coelestium", the epochal exposition of Copernican heliocentrism published in 1543. Throughout his explanatory canons, Reinhold used as his paradigm the position of Saturn at the birth of the Duke, on 17 May 1490. With these tables, Reinhold intended to replace the Alfonsine Tables; he added redundant tables to his new tables so that compilers of almanacs familiar with the older Alfonsine Tables could perform all the steps in an analogous manner.
Hydrography
Under Captain Thomas Hurd the department received its first professional guidelines, and the first catalogues were published and made available to the public and to other nations as well. In 1829, Rear-Admiral Sir Francis Beaufort, as Hydrographer, developed the eponymous Scale, and introduced the first official tide tables in 1833 and the first "Notices to Mariners" in 1834. The Hydrographic Office underwent steady expansion throughout the 19th century; by 1855, the Chart Catalogue listed 1,981 charts giving a definitive coverage over the entire world, and produced over 130,000 charts annually, of which about half were sold.
Geologic time scale
British geologists were also responsible for the grouping of periods into eras and the subdivision of the Tertiary and Quaternary periods into epochs. In 1841 John Phillips published the first global geologic time scale based on the types of fossils found in each era. Phillips' scale helped standardize the use of terms like "Paleozoic" ("old life") which he extended to cover a larger period than it had in previous usage, and "Mesozoic" ("middle life") which he invented.
Toledan Tables
The Tables of Toledo were partly based on the work of al-Zarqali (known to the West as Arzachel), an Arab mathematician, astronomer, astronomy instrument-maker, and astrologer, who lived in Toledo. The tables were produced by a team whose membership is largely unknown, with the exception of al-Zarqali. Toledo came under Christian Spanish rule in the mid-1080s, shortly after the tables were completed. A century later at Toledo, the Arabic-to-Latin translator Gerard of Cremona (1114–1187) translated for Latin readers the "Tables of Toledo", the most accurate compilation in Europe at the time. During the mid-thirteenth century, Campanus of Novara constructed tables for the meridian of Novara from the Toledan tables of al-Zarqali.
Periodic table
Following the discovery, in 1911, by Ernest Rutherford of the atomic nucleus, it was proposed that the integer count of the nuclear charge is identical to the sequential place of each element in the periodic table. In 1913, Henry Moseley using X-ray spectroscopy confirmed this proposal experimentally. Moseley determined the value of the nuclear charge of each element and showed that Mendeleev's ordering actually places the elements in sequential order by nuclear charge. Nuclear charge is identical to proton count and determines the value of the atomic number ("Z") of each element. Using atomic number gives a definitive, integer-based sequence for the elements. Moseley predicted, in 1913, that the only elements still missing between aluminium ("Z" = 13) and gold ("Z" = 79) were "Z" = 43, 61, 72, and 75, all of which were later discovered. The atomic number is the absolute definition of an element and gives a factual basis for the ordering of the periodic table. The periodic table is used to predict the properties of new synthetic elements before they are produced and studied.
Harmonic table note layout
The structure and properties of the Harmonic Table have been well known since at least the 18th century. Indeed, as a pitch space, the Harmonic Table is topologically equivalent to Euler's Tonnetz, discovered by the Swiss mathematician Leonhard Euler in 1739. The two pitch arrays are trivially obtained from each other by direct shear mapping. This note layout created by Euler is utilised in Neo-Riemannian theory to geometrically model its musical ideas.
Iguvine Tablets
The Iguvine Tablets, also known as the Eugubian Tablets or Eugubine Tables, are a series of seven bronze tablets from ancient Iguvium (modern Gubbio), Italy. The earliest tablets, written in the native Umbrian alphabet, were probably produced in the 3rd century BC, and the latest, written in the Latin alphabet, from the 1st century BC. The tablets contain religious inscriptions that memorialize the acts and rites of the Atiedian Brethren, a group of 12 priests of Jupiter with important municipal functions at Iguvium. The religious structure present in the tablets resembles that of the early stage of Roman religion, reflecting the Roman archaic triad and the group of gods more strictly related to Jupiter. Discovered in a farmer's field in the year 1444, they are currently housed in the Civic Museum of the Palazzo dei Consoli in Gubbio.
Paul-Antoine Giguère
In 1966 he proposed a novel three-dimensional arrangement of the periodic table.
Rime table
The oldest known rhyme tables are a version of the "Yunjing" published with prefaces dated 1161 and 1203, and the "Qiyin lüe", which was included in the 1161 encyclopedia "Tongzhi". The two are very similar, and are believed to be derived from a single version pre-dating the Song dynasty. The tables were accompanied by a body of teachings known as "mēnfǎ" (), including rules for placing fanqie spellings that did not conform to the system within the tables.
Tables (board game)
The τάβλη of Zeno's time is believed to be a direct descendant of the earlier ancient Roman "Ludus duodecim scriptorum" ("game of twelve lines" or, better, "game of twelve signs") with that board's middle row of points removed, and only the two outer rows remaining. Ludus duodecim scriptorum used a board with three rows of 12 points each, and the pieces were moved across all three rows according to the roll of three dice. The earliest known mention of the game is in Ovid's "Ars Amatoria" ("The Art of Love") (written between 1 BC and 8 AD).
In the 11th century Shahnameh, the Persian poet Ferdowsi credits Burzoe with the invention of "nard" in the 6th century. He describes an encounter between Burzoe and a Raja visiting from India. The Raja introduces the game of chess, and Burzoe demonstrates nard, played with dice made from ivory and teak.
Rainbow table
Rainbow tables were invented by Philippe Oechslin as an application of an earlier, simpler algorithm by Martin Hellman.
Thomas Fale
His only known publication is "Horologiographia" (1593). It is dedicated in Latin to all lovers of mathematics in the University of Cambridge. There is also a prefatory letter to ‘my louing kinsman,’ Thomas Osborne, who had invented the instrument mentioned in the beginning of the book ‘for the triall of plats,’ dated from London, 3 January 1593. The table of sines which it contains is probably the earliest specimen of a trigonometrical table printed in England.
De revolutionibus orbium coelestium
Among some astronomers, the book "at once took its place as a worthy successor to the "Almagest" of Ptolemy, which had hitherto been the Alpha and Omega of astronomers". Erasmus Reinhold hailed the work in 1542 and by 1551 had developed the "Prutenic Tables" ("Prussian Tables"; ; ) using Copernicus' methods. The "Prutenic Tables", published in 1551, were used as a basis for the calendar reform instituted in 1582 by Pope Gregory XIII. They were also used by sailors and maritime explorers, whose 15th-century predecessors had used Regiomontanus' "Table of the Stars". In England, Robert Recorde, John Dee, Thomas Digges and William Gilbert were among those who adopted his position; in Germany, Christian Wurstisen, Christoph Rothmann and Michael Mästlin, the teacher of Johannes Kepler; in Italy, Giambattista Benedetti and Giordano Bruno whilst Franciscus Patricius accepted the rotation of the Earth. In Spain, rules published in 1561 for the curriculum of the University of Salamanca gave students the choice between studying Ptolemy or Copernicus. One of those students, Diego de Zúñiga, published an acceptance of Copernican theory in 1584.
Chemical affinity
The affinity concept was very closely linked to the visual representation of substances on a table. The first-ever "affinity table", which was based on displacement reactions, was published in 1718 by the French chemist Étienne François Geoffroy. Geoffroy's name is best known in connection with these tables of "affinities" ("tables des rapports"), which were first presented to the French Academy of Sciences in 1718 and 1720, as shown below:
History of the periodic table
The Russian chemist Dmitri Mendeleev arranged the elements by atomic mass, corresponding to relative molar mass. It is sometimes said that he played 'chemical solitaire' on long train journeys, using cards with various facts about the known elements. On March 6, 1869, Mendeleev gave a formal presentation, "The Dependence Between the Properties of the Atomic Weights of the Elements", to the Russian Chemical Society. In 1869, the table was published in an obscure Russian journal and then republished in a German journal, "Zeitschrift für Chemie". In it, Mendeleev stated that:Scientific benefits of Mendeleev's tableIn 1864, the English chemist William Odling also drew up a table that was remarkably similar to the table produced by Mendeleev. Odling overcame the tellurium-iodine problem and even managed to get thallium, lead, mercury and platinum into the right groups, which is something that Mendeleev failed to do at his first attempt.
Odling failed to achieve recognition, however, since it is suspected that he, as Secretary of the Chemical Society of London, was instrumental in discrediting Newlands' earlier work on the periodic table.By 1912 almost 50 different radioactive elements had been found, too many for the periodic table. Frederick Soddy in 1913 found that although they emitted different radiation, many elements were alike in their chemical characteristics so shared the same place on the table. They became known as isotopes, from the Greek "" ("same place").
Periodic systems of small molecules
Periodic systems of molecules are charts of molecules similar to the periodic table of the elements. Construction of such charts was initiated in the early 20th century and is still ongoing.
Periodic table
The various forms of periodic tables can be thought of as lying on a chemistry–physics continuum. Towards the chemistry end of the continuum can be found, as an example, Rayner-Canham's "unruly" Inorganic Chemist's Periodic Table (2002), which emphasizes trends and patterns, and unusual chemical relationships and properties. Near the physics end of the continuum is Janet's Left-Step Periodic Table (1928). This has a structure that shows a closer connection to the order of electron-shell filling and, by association, quantum mechanics. A somewhat similar approach has been taken by Alper, albeit criticized by Eric Scerri as disregarding the need to display chemical and physical periodicity. Somewhere in the middle of the continuum is the ubiquitous common or standard form of periodic table. This is regarded as better expressing empirical trends in physical state, electrical and thermal conductivity, and oxidation numbers, and other properties easily inferred from traditional techniques of the chemical laboratory. Its popularity is thought to be a result of this layout having a good balance of features in terms of ease of construction and size, and its depiction of atomic order and periodic trends.
Rudolphine Tables
Star tables had been produced for many centuries and were used to establish the position of the planets relative to the fixed stars (particularly the twelve constellations used in astrology) on a specific date in order to construct horoscopes. Until the end of the 16th century, the most widely used had been the "Alphonsine tables", first produced in the 13th century and regularly updated thereafter. These were based on a Ptolemaic, geocentric model of the Solar System. Although the Alphonsine tables were not very accurate, nothing else was available and so they continued to be used.
Alternative periodic tables
Charles Janet's Left step periodic table (1928) is considered to be the most significant alternative to the traditional depiction of the periodic system. It organizes elements according to orbital filling (instead of valence) and is widely used by physicists.
Tropical year
In the 16th century Copernicus put forward a heliocentric cosmology. Erasmus Reinhold used Copernicus' theory to compute the Prutenic Tables in 1551, and gave a tropical year length of 365 solar days, 5 hours, 55 minutes, 58 seconds (365.24720 days), based on the length of a sidereal year and the presumed rate of precession. This was actually less accurate than the earlier value of the Alfonsine Tables.
Beda Venerabilis' Easter cycle
In the year 616 an anonymous scholar extended Dionysius Exiguus' Easter table to an Easter table covering the years 532 up to and including 721. Dionysius' table was published in 525 and only a century later accepted by the church of Rome, which from the third century up till then had given preference to go on using her own, relatively inadequate, Easter tables. From about the middle of the seventh century all controversy between Alexandria and Rome as to the correct date of Easter ceased, as both churches were now using identical tables.
Pier table
The pier table takes its English name from the "pier wall", the space between windows. The table was developed in continental Europe in the 1500s and 1600s, and became popular in England in the last quarter of the 1600s. The pier table became known in North America in the mid-1700s, and was a popular item into the mid to late 1800s. It was common for the space between the rear legs of the pier table to contain a mirror, or "pier glass", to help hide the wall. Later pier tables were designed to stand in any niche in a room, and the pier glass moved above the table.
Abū Ishāq Ibrāhīm al-Zarqālī
Al-Zarqālī also contributed to the famous "Tables of Toledo", an adaptation of earlier astronomical data to the location of Toledo along with the addition of some new material. Al-Zarqālī was famous as well for his own "Book of Tables." Many "books of tables" had been compiled, but his almanac contained tables which allowed one to find the days on which the Coptic, Roman, lunar, and Persian months begin, other tables which give the position of planets at any given time, and still others facilitating the prediction of solar and lunar eclipses.
History of the periodic table
Moseley's research showed that there were gaps in the periodic table at atomic numbers 43 and 61, which are now known to be occupied by technetium and promethium respectively.
Periodic table
In 1871, Mendeleev published his periodic table in a new form, with groups of similar elements arranged in columns rather than in rows, and those columns numbered I to VIII corresponding with the element's oxidation state. He also gave detailed predictions for the properties of elements he had earlier noted were missing, but should exist. These gaps were subsequently filled as chemists discovered additional naturally occurring elements. It is often stated that the last naturally occurring element to be discovered was francium (referred to by Mendeleev as "eka-caesium") in 1939. Plutonium, produced synthetically in 1940, was identified in trace quantities as a naturally occurring element in 1971.
Toledan Tables
The Toledan Tables, or Tables of Toledo, were astronomical tables which were used to predict the movements of the Sun, Moon and planets relative to the fixed stars. They were completed around year 1080 by a group of Arabic astronomers at Toledo, Spain. They had started as preexisting Arabic tables made elsewhere, and were numerically adjusted to be centered on the location of Toledo. In modern English astronomy, tables of movements of astronomical bodies are called ephemerides.
Leopold Gmelin
Leopold Gmelin besides also developed a forerunner of the Periodic table and improved chemical equipment.
Emerald Tablet
C.G. Jung identified "The Emerald Tablet" with a table made of green stone which he encountered in the first of a set of his dreams and visions beginning at the end of 1912, and climaxing in his writing "Seven Sermons to the Dead" in 1916. Historians of science, Eric John Holmyard (1891–1959) and Julius Ruska (1867–1949) also studied the tablet in the twentieth century. Because of its longstanding popularity, the "Emerald Tablet" is the only piece of non-Greek Hermetica to attract widespread attention in the West.
Thorium
In the periodic table published by Dmitri Mendeleev in 1869, thorium and the rare-earth elements were placed outside the main body of the table, at the end of each vertical period after the alkaline earth metals. This reflected the belief at that time that thorium and the rare-earth metals were divalent. With the later recognition that the rare earths were mostly trivalent and thorium was tetravalent, Mendeleev moved cerium and thorium to group IV in 1871, which also contained the modern carbon group (group 14) and titanium group (group 4), because their maximum oxidation state was +4. Cerium was soon removed from the main body of the table and placed in a separate lanthanide series; thorium was left with group 4 as it had similar properties to its supposed lighter congeners in that group, such as titanium and zirconium.