The development of the periodic table of the elements 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 47 elements had been discovered, and by 1863, 56 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.
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.
Berzelius was a Swedish chemist. In 1828 he compiled a table of relative atomic weights, where oxygen was set to 100, and which included all of the elements known at the time. Of significance for the periodic table is that he invented the modern system of chemical notation and established the basic symbols for the elements as used today. In this system elements are given symbols, and compounds represented by combining element symbols and numbers representing proportions. Students working in Berzelius laboratory are credited with discovering lithium, and vanadium. Other elements attributed to Berzelius are silicon, selenium, thorium, and cerium. Together with John Dalton and Antoine Lavoisier he is considered a father of modern chemistry.
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.
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. 
John Newlands was an English chemist who wrote a paper in 1863 that 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.
As the number of known elements increased two men working independently created the first periodic tables at about the same time. These two were Julius Lothar Meyer and Dimitri Mendeleev. Meyer published some data first, but didn't publish a table till a few months after Mendeleev. Meyer and Mendeleyev can be considered the cocreators of the periodic table, though most agree that Mendeleyev's accurate predictions land him the larger share of credit. At the time it was Mendeleev's predictions that greatly impressed his contemporaries especially when they were eventually found to be correct.
Meyer was contemporary with Mendeleev; he 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. Meyer was examining the physical properties of the elements and noticed a periodicity in their molar volume.
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 similar to Mendeleev's.
Dmitri Mendeleev, (also spelled Mendeleyev, middle name (patronymic) Ivanovich, was a Siberian-born Russian chemist. Mendeleev was investigating the variation in the chemical properties of the elements (see image at right) and noticed their periodic variation. He 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 initially published in an obscure Russian journal but quickly republished in a German journal, Zeitschrift für Chemie, in 1869.
Mendeleev's work stated
|56, 59, 59
Fe, Co, Ni
|104, 104, 106
Ru, Rh, Pd
|195, 197, 198
Os, Ir, Pt
|Group I||Group II||Group III||Group IV|
|Group V||Group VI||Group VII||Group VIII|
Mendeleev used his table to predict properties and the existence of other new elements (? in table above). He left space for these new elements, eka-silicon (germanium), eka-aluminum (gallium), and eka-boron (scandium), in his table. He pointed out that some of the then current atomic weights were incorrect and provided for variance from atomic weight order
On the evening of April 19, 1894, William Ramsay attended a lecture given by Lord Rayleigh. Rayleigh had noticed a discrepancy between the density of nitrogen made by chemical synthesis and nitrogen isolated from the air by removal of the other known components. After a short discussion he and Ramsay decided to follow this up. By August Ramsay could write to Rayleigh to announce that he had isolated a heavy component of air previously unknown which did not appear to have any obvious chemical reactivity. He named the gas "argon." In the years that followed he discovered neon, krypton, and xenon. He also isolated helium which had been observed in the spectrum of the sun but had not been found on earth. In 1910 he also isolated and characterized radon.
These noble gasses were initially incorporated into Mendeleev's table as a zero group and placed before the group I elements of each period.
The early part of the twentieth century saw rapid advances in our understanding of the structure of matter and concomitantly changes in the periodic table. The noble gasses were placed at the end of the periods rather than at the beginning. Periods four and up were found to be longer than one through three as the transition metals were placed correctly, and the shorter periods were divided.
In 1911 Rutherford demonstrated that atoms had a nucleus where most of the mass and all the positive charge of the atom resided. The nuclear charge, or atomic number (the number of protons in the nucleus}, became the organizing principle of the table.
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 demonstrated that the ordering of elements in the table should be according to atomic number not atomic weight. This resolved some issues that even Mendeleev had been aware of. His work also showed that there were gaps in the table at atomic numbers 43 and 61 that are now known to be radioactive and not naturally occurring. Following in the footsteps of Dmitriy Mendeleyev, Henry Moseley also predicted new elements.
Of Swedish ancestry, Seaborg was born in Ishpeming, Michigan. He received a bachelor's degree in chemistry at the University of California, Los Angeles in 1934. He took his doctorate in chemistry (even though his dissertation was in physics) at the University of California, Berkeley, in 1937. In 1939 he became an instructor in chemistry at Berkeley, was promoted to professor in 1945, and served as chancellor from 1958 to 1961.
In his early research, he utilized cyclotron bombardment to create more than 50 atomic isotopes including several still used in medical applications today. In 1941 he is credited with discovering and isolating plutonium, and subsequently the transuranic elements from atomic number 94 through 102. His work in the transuranic elements led to a reconfiguration of the periodic table where he placed the actinide series below the lanthanide series at the bottom of the table, to give the periodic table the look it has today.
In recognition of his contributions, element 106 was called seaborgium in his honor.
All links retrieved February 26, 2014.
|Standard table | Vertical table | Table with names | Names and atomic masses (large) | Names and atomic masses (small) | Names and atomic masses (text only) | Inline F-block | Elements to 218 | Electron configurations | Metals and non metals | Table by blocks | List of elements by name|
|Groups: 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 - 13 - 14 - 15 - 16 - 17 - 18|
|Periods: 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8|
|Series: Alkalis - Alkaline earths - Lanthanides - Actinides - Transition metals - Poor metals - Metalloids - Nonmetals - Halogens - Noble gases|
|Blocks: s-block - p-block - d-block - f-block - g-block|
|General subfields within the Natural sciences|
|Astronomy | Biology | Chemistry | Earth science | Ecology | Physics|
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