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Atomic Elements
Things are different from each other, and each can be reduced to very small parts of itself. - Ancient knowledge This was noticed early by people, and Greek thinkers, about 400BC, used the words "element', and `atom' to describe the differences and smallest parts of matter. These ideas survived for 2000 years while concepts such as `Elements' of Earth, Fire, Air, and Water to explain `world stuff' came and went. Much later, Boyle, an experimenter like Galileo and Bacon, and who was influenced much by Democritus, Gassendi, and Descartes, lent important weight to the atomic theory of matter in the 1600s. It was Lavoisier who divided the few elements known in the 1700's into four classes, and then John Dalton made atoms even more convincing, suggesting that the mass of an atom was it's most important property. "The chemical elements are composed of... indivisible particles of matter, called atoms... atoms of the same element are identical in all respects, particularly weight." - Dalton In the early 1800's Dobereiner noted that similar elements often had relative atomic masses, and DeChancourtois made a cylindrical table of elements to display the periodic reoccurrence of properties. Cannizaro determined atomic weights for the 60 or so elements known in the 1860s, then a table was arranged by Newlands, with the elements given a serial number in order of their atomic weights, beginning with Hydrogen. This made evident that "the eighth element, starting from a given one, is a kind of repetition of the first", which Newlands called the Law of Octaves. Both Meyer and Mendeleyev constructed periodic tables independently, Meyer more impressed by the periodicity of physical properties, while Mendeleyev was more interested in the chemical properties. "...if all the elements be arranged in order of their atomic weights a periodic repetition of properties is obtained." - Mendeleyev Mendeleyev p... Please login to view comments from other users.
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