Atomic Theory.

Aristotle: -believed that atoms were made from the 4 elements; earth, air, fire, and water Democritus: -in 300B.C, he believed that atoms were indivisible particles
Lavoisier (late 1700's) -stated earliest version of both the Law of Conservation and the Law of definite proportions
Proust (1799) - Proust believed that if a compound were to be broken down, it would still contain the same ratios as in the compound
Dalton (early 1800's) - believed that atoms are solid
-all atoms of given element are identical
-atoms of one element can combine with another to form chemical compounds
J.J. Thompson (1850) - proved existance of electrons
Rutherford (1905) - showed atoms had dense centres and electrons outside of them
-suggested atoms are mostly empty space
Niels Bohr (1885-1962) - studied gaseous samples of atoms
-proposed that electrons surrounds the nucleus in shells
The modern atom - an atom is the smallest particle of an element
-all atoms are made of three kinds of subatomic particles
         -electrons
         -protons
         -neutrons