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Small history of elements classification

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Last modified on: August 22th 2018

democrite Democrite, thinker of the Vth century BC, taking back to his master Leucippe talks, suggest an atomic theory: Matter is made from non-divisible particles ("atomos" in greek).
empedocle In the IVth century BC, Empedocle, contrarily to Democrite talks suggest this theory:

Universe is made from four elements :

  • Earth
  • Water
  • Air
  • Fire
aristote At the same periode, Aristote strength the theory by adding four qualitys to the four elements: cold, dry, hot, wet.

Those qualitys in couple form elements, who form the universe.

This theory reach to explain some freaks of nature.

Short model of aristote

Source : Cyberscol

23 century later...
daltonIn 1808, John Dalton, chemist and physician, rewrite and make deeper atomic theory of democrite:

  • Matter is made of infinitely small and non divisible particles called atoms.
  • All atoms of a same element are identicals, same proprerty and mass.
mendeleiev In 1869 Dimitri Ivanovitch Mendeleïev, chemistry professor in St-Petersburg classify elements according to their propertys.

Writing a chemistry book, he discover that sorting elements by their atomic mass, a cyclic trend of their propertys appear several times.

First table of mendeleiev

First Mendeleïev table

Mendeleïev make his table so that periodicity appear clearly, but to respect his periodicity law in which he trust, he must sometimes modify order and let some cells empty.

He was sure that those missing elements will be finally discovered, and so predict the properys of those futur elements (according to the adjacents cells in the table): eka-aluminium, eka-bore and eka-silicium.

Between 1875 and 1886, those three elements (gallium, scandium and germanium) where discovered. Each of them had the property predicted by Mendeleïev.

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