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Democritus
1.All matter consists of invisible particles called atoms.
2. Atoms are indestructible.
3. Atoms are solid but invisible.
4. Atoms are homogenous.
5. Atoms differ in size, shape, mass, position, and arrangement.
->Solids are made of small, pointy atoms.
->Liquids are made of large, round atoms.
->Oils are made of very fine, small atoms that can easily slip past each other. -
John 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.
1803-1810 -
JJ Thomson
He discovered the electron through a series of experiment, and also suggested a model of the atom as sphere of positive matter surrounded by electrons which are positioned by electrostatic forces. He developed the “plum pudding model” of an atom
1897-1904 -
Robert Milliken
Accurately determined the charge carried by an electron, using the “fall drop method”, and he also determined this was constant for all electrons -
Ernst Rutherford
Rutherford tested Thomson’s hypothesis by doing his “gold foil” experiment. He developed the planetary model of the atom. -
Neils Bohr
He proposed a theory that energy is only transferred in certain defined quantities -
Jamed Chadwick
Chadwick discovered the neutron using evidence from other scientists experiment
