Democritus+and+Dalton

=Democritus=

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 * Greek philosopher (460-370 BC)
 * thought that everything in the material world must be made up of tiny indivisible particles.
 * called particles atomos, which means indivisible.
 * Plato and Aristotle formulated that there can be no indivisible particles.

=John Dalton= ==

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 * 1766-1844
 * English chemist, meteorologist, and physicist.
 * Reasoned the atomic theory around 1803-1807
 * From a large number of observations, Dalton made the Four Postulates:


 * 1) Each element is composed of //extremely small// particles called atoms.
 * 2) All atoms of a given element are identical; different elements have different atoms and different properties, including masses.
 * 3) Atoms of an element are not changed into different types of atoms by chemical reactions; atoms are neither created nor destroyed in chemical reactions.
 * 4) Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kind of atoms.