Difference between revisions of "History of the periodic table" - New World Encyclopedia

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The development of the periodic table parallels the development of science and our understanding of the physical universe. It is central to our current understanding of the "stuff" we are all made from. The earliest attempts to understand matter were primarily philosophical without recourse to strict experimental verification. Thus, although some of the chemical elements have been known since antiquity there was no attempt to systematically arrange them according to their properties.

As science developed through the eighteenth and nineteenth centuries the rate of discovery of new elements increased. By 1809, a total of forty seven elements had been discovered, and by 1863 fifty six were known. As the number of known elements grew, scientists began to recognize patterns in their properties and began to devise ways to classify them.

Anotoine Laurent de Lavoisier

Antoine-Laurent de Lavoisier

Lavoisier's Traité Élémentaire de Chimie (Elementary Treatise of Chemistry, 1789, translated into English by Robert Kerr) is considered to be the first modern chemical textbook. It contained a list of elements, or substances that could not be broken down further, which included oxygen, nitrogen, hydrogen, phosphorus, mercury, zinc, and sulfur. It also forms the basis for the modern list of elements. His list, however, also included light and caloric, which he believed to be material substances. While many leading chemists of the time refused to believe Lavoisier's new revelations, the Elementary Treatise was written well enough to convince the younger generation.

Johann Wolfgang Döbereiner

Döbereiner was a German chemist. As a coachman's son, he had little opportunity for formal schooling, but was apprenticed to an apothecary, read widely, and attended science lectures. Eventually from 1810 he was professor of the University of Jena. He discovered furfural, worked on the use of platinum as a catalyst, and invented a lighter, known as Döbereiner's Lamp. With regard to the periodic table he is known especially for his discovery of triads of elements in 1829. He identified groups of three chemically similar elements that today we understand fall in the same group or family of the periodic table.

**Some triads**
Element	Molar mass (g/mol)	Density (g/cm³)	Quotient (cm³/mol)
chlorine	35.4527	0.003214	11030
bromine	79.904	3.122	25.6
iodine	126.90447	4.93	25.7

calcium	40.078	1.54	26.0
strontium	87.62	2.64	33.2
barium	137.327	3.594	38.2

Alexandre-Emile Béguyer de Chancourtois

Alexandre-Emile Béguyer de Chancourtois, a French geologist, was the first person to notice the periodicity of the elements — similar elements seem to occur at regular intervals when they are ordered by their atomic weights. He devised an early form of periodic table, which he called the telluric helix. With the elements arranged in a spiral on a cylinder by order of increasing atomic weight, de Chancourtois saw that elements with similar properties lined up vertically. His chart included some ions and compounds in addition to elements. His paper was published in 1862, but 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. [1]

John Newlands' Octaves

John Newlands was an English chemist who wrote a paper in 1863 which classified the 56 elements that had been discovered at the time into 11 groups which were based on similar physical properties. He noted that many pairs of similar elements existed which differed by some multiple of eight in atomic weight.

Newlands took Döbereiner's ideas and expanded on them. He also organized his elements by mass and property, but he added a twist. Döbereiner had worked only in small groups, but Newlands wanted to relate all the elements to each other.

Newlands arranged the known elements in a table by atomic weights. In doing so, he noticed some recurring patterns, and the patterns were such that if he broke up his list of elements into groups of seven, the first elements in each of those groups were similar to one another, as was the second element in each group, and the third, and so on. By analogy with the tonic musical scale of seven notes, which form octaves, he called his discovery the Law of Octaves.

Newlands also noticed that silicon and tin formed part of a triad and so predicted a third unknown element with atomic weight of about 73, anticipating Mendeleev's prediction of germanium by six years, but did not leave a space for the new element in his table.

Newlands' work was heavily criticized, even ridiculed, by other chemists, because of the lack of spaces for undiscovered elements and the placing of two elements in one box, but he was finally awarded the Davy Medal by the Royal Society in 1887.

Julius Lothar Meyer

Meyer was contemporary with Dmitri Mendeleev and competed with him to draw up the first periodic table of chemical elements. Meyer qualified in medicine at Zürich, Switzerland, and then studied and taught at various German universities. Thought his first interest was physiology he was primarily interested in chemistry.

In 1864, Meyer published a preliminary list of 28 elements classified into 6 families by their valence—this was the first time that the elements had been grouped and ordered according to their valence. Work on organizing the elements by atomic weight had hitherto been stymied by inaccurate measurements of the atomic weights. Then in 1868 he prepared an expanded version, and in 1870 published his list as a table that in many ways was similer to Mendeleev's.

Dmitri Mendeleev

One form of Mendeleev's periodic table, from the 1st English edition of his textbook (1891, based on the Russian 5th edition)

Dmitri Mendeleev, also spelt Dmitry Mendeleyev, middle name (patronymic) Ivanovich, a Siberian-born Russian chemist, was the first scientist to make a periodic table much like the one we use today. Mendeleev arranged the elements in a table ordered by atomic mass. On March 6, 1869, a formal presentation was made to the Russian Chemical Society, entitled The Dependence Between the Properties of the Atomic Weights of the Elements. His table was published in an obscure Russian journal but quickly republished in a German journal, Zeitschrift für Chemie, in 1869. It stated

The elements, if arranged according to their atomic weights, exhibit an apparent periodicity of properties.
Elements which are similar as regards to their chemical properties have atomic weights which are either of nearly the same value (e.g., Pt, Ir, Os) or which increase regularly (e.g., K, Rb, Cs).
The arrangement of the elements, or of groups of elements in the order of their atomic weights, corresponds to their so-called valencies, as well as, to some extent, to their distinctive chemical properties; as is apparent among other series in that of Li, Be, Ba, C, N, O, and Sn.
The elements which are the most widely diffused have small atomic weights.
The magnitude of the atomic weight determines the character of the element, just as the magnitude of the molecule determines the character of a compound body.
We must expect the discovery of many as yet unknown elements–for example, elements analogous to aluminum and silicon–whose atomic weight would be between 65 and 75.
The atomic weight of an element may sometimes be amended by a knowledge of those of its contiguous elements. Thus the atomic weight of tellurium must lie between 123 and 126, and cannot be 128.
Certain characteristic properties of elements can be foretold from their atomic weights.

Mendeleev's periodic table

Advantages

Mendeleev predicted the discovery of other elements and left space for these new elements, namely eka-silicon (germanium), eka-aluminum (gallium), and eka-boron (scandium). Thus, there was no disturbance in the periodic table.
He pointed out that some of the then current atomic weights were incorrect.
He provided for variance from atomic weight order

Drawbacks

There was no place for the isotopes of the various elements.
His table did not include any of the noble gases, which hadn't been discovered. But these could be added in another group without any disturbance to the periodic table.

Group →	I	II	III	IV	V	VI	VII	VIII
Period ↓
1	1 H
2	7 Li	9.4 Be	11 B	12 C	14 N	16 O	19 F
3	23 Na	24 Mg	27.3 Al	28 Si	31 P	32 S	35.5 Cl
4	39 K	40 Ca	44 ?	48 Ti	51 V	52 Cr	55 Mn	56, 59, 59 Fe, Co, Ni
5	63 Cu	65 Zn	68 ?	72 ?	75 As	78 Se	80 Br
6	85 Rb	87 Sr	88 ?Yt	90 Zr	94 Nb	96 Mo	100 ?	104, 104, 106 Ru, Rh, Pd
7	108 Ag	112 Cd	113 In	118 Sn	122 Sb	125 Te	127 I
8	133 Cs	137 Ba	138 ?Di	140 ?Ce
9
10			178 ?Er	180 ?La	182 Ta	184 W		195, 197, 198 Os, Ir, Pt
11	199 Au	200 Hg	204 Tl	207 Pb	208 Bi
12				231 Th		240 U

Groups of Mendeleev's Table
Group I	Group II	Group III	Group IV
Group V	Group VI	Group VII	Group VIII

Unknown to Mendeleyev, Lothar Meyer was also working on a periodic table. In his work published in 1864, Meyer presented only 28 elements, classified not by atomic weight but by valence alone. Also, Meyer never came to the idea of predicting new elements and correcting atomic weights. Only a few months after Mendeleev published his periodic table of all known elements (and predicted several new elements to complete the table, plus some corrected atomic weights), Meyer published a virtually identical table. Some people consider Meyer and Mendeleyev the cocreators of the periodic table, although most agree that Mendeleyev's accurate prediction of the qualities of what he called lands him the larger share of credit. In any case, at the time Mendeleyev's predictions greatly impressed his contemporaries and were eventually found to be correct. An English chemist, William Odling, also drew up a table that is remarkably similar to that of Mendeleyev in 1864.

Henry Moseley

In 1913, Henry Moseley found a relationship between an element's X-ray wavelength and its atomic number. Before this discovery, atomic numbers were just random numbers based on an element's atomic weight. Moseley's discovery showed that atomic numbers were not arbitrary but had an experimentally measurable basis.

Mosley's research also showed that there were gaps in his table at atomic numbers 43 and 61 which are now known to be radioactive and not naturally occurring. Following in the footsteps of Dmitriy Mendeleyev, Henry Moseley also predicted new elements.

Walter Russell

Curiously, Walter Russell produced yet another periodic table in 1926, complaining that the widely accepted table did (as it does indeed) have gaps and exceptions which are not scientific. This table predicted the existence of several then undiscovered elements, including tritium, deuterium, plutonium, and neptunium. This table never gained widespread acceptance, though it's still touted by a devout following for its "completeness", lacking the need for special exceptions of the official table.

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@@ Line 80: / Line 80: @@
 * His table did not include any of the [[noble gas]]es, which hadn't been discovered. But these could be added in another group without any disturbance to the periodic table.
+{{Mendeleev table}}
 Unknown to Mendeleyev, [[Lothar Meyer]] was also working on a periodic table. In his work published in 1864, Meyer presented only 28 elements, classified not by [[atomic weight]] but by [[Valence (chemistry)|valence]] alone. Also, Meyer never came to the idea of predicting new elements and correcting atomic weights. Only a few months after Mendeleev published his periodic table of all known elements (and predicted several new elements to complete the table, plus some corrected atomic weights), Meyer published a virtually identical table. Some people consider Meyer and Mendeleyev the cocreators of the periodic table, although most agree that Mendeleyev's accurate prediction of the qualities of what he called lands him the larger share of credit. In any case, at the time Mendeleyev's predictions greatly impressed his contemporaries and were eventually found to be correct.  An English chemist, [[William Odling]], also drew up a table that is remarkably similar to that of Mendeleyev in 1864.