Atomic Theory

History of Atomic Theory

Aristotle

322 - 384

Believed in five elements Earth, Water, Fire, Air, Aether- planets , sun, stars

Democritus

371 - 460

Believed all matter consisted of extremely small particles that could not be divided

John Dalton

1700

Came up with the first atomic theory

Joseph John Thompson

1856 - 1940

Discovered the electron was negitive

Millikan

1868 - 1953

Conducted an Experiment to determin the mass of the electreon.He placed drops between an electrical feild and determined the precise mass of an electron at 1\1837.

Ernest Ruthford

1871 - 1937

Proposed the orbital view of the atom

James Chadwick

1891 - 1974

He won the nobel prize for discovering the neutron. The neutron is neutral and has a mass of 1.008665 amu or simply 1.