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Copy of Timeline: Development of the Modern Periodic Table

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Devika Raju

on 15 October 2013

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Transcript of Copy of Timeline: Development of the Modern Periodic Table

Timeline: Development of the Modern Periodic Table
In 1869, Mendeleev formulated the periodic law and published the periodic table in the Principles of Chemistry. He predicted the existence of properties of three elements that were later discovered. He established that atomic weight could be used to arrange the elements and their groups. He discovered the periodic law and wrote and published ‘The Relation of the Properties to the Atomic Weight of the Elements’ in 1870 that showed the valence of each element and how it linked a family together. This allowed for his formation of a systematic table of 70 elements. He understood that the atomic mass and physical/chemical properties of elements are related. He arranged them into vertical columns that held groups of elements with similar properties. He found errors in the accepted atomic weights of some elements, too.
Flaws / Reasons Theory wasn't used
Dobereiner’s triads weren’t used because other scientists went on to find that the relations between elements could involve more than just three elements. They eventually configured different structures and arrangements of the increasing discovery of new elements to form a more effective periodic table rather than using triads.
Johann Wolfgang Dobereiner
Johann Dobereiner discovered the existence of families of three elements with similar chemical properties and patterns in physical properties (such as atomic mass and number, appearance, melting/boiling point, and reactions). He developed the Law of Triads after finding that Strontium had the average properties of Calcium and Barium. He grouped these three together to form a triad. Dobereiner eventually made several other triad groups including the Halogen triad of Chlorine, Bromine, and Iodine, and the Alkali Metal triad of Lithium, Sodium, and Potassium.
Johann Wolfgang Dobereiner
John Alexander Reina Newlands
Based on the increasing order of their atomic weight, Newlands arranged elements in a table, while also discovering that every eighth element exhibited similar characteristics like the eight note of an octave in music. He proposed the Law of Octaves in a paper which stated that an element displays behavior similar to the eighth element before and after it.
John Alexander Reina Newlands
Flaws / Reasons Theory wasn't used
His grouping of elements was flawed. For example, a metal was grouped with two nonmetals. Also, his table lacked space for new or undiscovered elements. His strong attempts to link it with music caused him to force the elements into this pattern, which created inaccuracies. Also, due to his rigid arrangement methods, two elements were sometimes placed into one box. In addition, his arrangement caused elements with different chemical properties to be grouped in the same row.
Julius Lothar Meyer
Meyer showed the relation between the atomic weights and properties of elements, and developed a periodic table based on this. In 1864, he published his first periodic table describing the placement of 28 elements into six families. By 1868, he developed a periodic table that listed elements in order of atomic weight. He grouped elements according to their valence. In 1870, he published a paper that described the evolution of his work from 1864 and included the graph of atomic mass plotted against atomic mass.
Julius Lothar Meyer
Flaws / Reasons Theory wasn't used
Meyer's arrangement was based on atomic weight (like Mendeleev) which eventually created problems. Also, incorrect measurements of the atomic weights caused inaccuracies. Because Mendeleev published his version a year before Meyer did, Meyer's table wasn't credited properly and was used less frequently.
Dmitri Ivanovich Mendeleev
Flaws / Reasons Theory wasn't used
Mendeleev’s periodic table’s structure was such that grouping elements by their properties wouldn’t always line them up in ascending atomic masses and vice versa. His table also did not include noble gases. His vertical columns are horizontal rows in our current periodic table structure. Also, modern periodic tables have broadened further with the discovery of new elements. Some of his elements were misplaced (ex: Rhodium).
Dmitri Ivanovich Mendeleev
Moseley first proposed the organizing principle of the periodic table to be based on atomic number and increasing nuclear charge rather than atomic mass. In 1913, he created Moseley’s Law, which stated that the periodic table should be arranged by atomic number, and published the results of his x-ray spectra readings, which showed the exact characteristics of the nucleus for each individual element. He also predicted some elements and their periodic numbers in the periodic table.
Henry Moseley
Flaws / Reason Theory wasn't used
So far, there are no known flaws to Henry Moseley’s system. The only changes to his table have been the addition of newly discovered elements.
Henry Moseley
Devika Raju
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