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400
Democritus
This man invented the atom. If he didnt find the atom hundreds of years ago we would still be searching. There also wouldnt be an atomic theory. -
Dalton
1) All matter is made of atoms. Atoms are indivisible and indestructible. 2) All atoms of a given element are identical in mass and properties 3) Compounds are formed by a combination of two or more different kinds of atoms. 4) A chemical reaction is a rearrangement of atoms. -
Modern Atomic Theory
All matter is composed of extremely small particles called atoms.
Atoms of a given element are identical in size, mass and other properties. Atoms of different elements differ in size, mass and other properties.
Atoms cannot be subdivided, created, or destroyed.
Atoms of different elements combine in simple whole number ratios.
In chemical reactions, atoms are combined, separated, or rearranged -
Thomson
He identified electrons as particals that are present in every atom. -
Rutherford
He was a physisist from New Zealand, He discovers the posotivily charged nucleous of the atom. -
Bohr
He was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory.
