Atomic Timeline

By: Ethan Scribano

People

Democritus

440 BC

Proposed that atoms constantly move.

John Dalton

1803

Atoms of different elements are different; Atoms are small, hard particles; He conducted experiments in combining elements; Atoms of the same element are exactly alike; All substances are made of atoms.

J. J. Thompson

1897

Proposed that there are small, negatively charged particles inside an atom;

Ernest Rutherford

1911

Proposed that there is a small, dense, positively charged nucleus; Most of an atom's mass is in the nucleus; Atoms contain mostly empty space; Electrons move in empty space in the atom; He conducted the gold foil experiment.

Niels Bohr

1913

Proposed that electrons jump between levels from path to path; Electron paths cannot be predicted; Electrons are found in electron clouds, not paths.

Schrodinger and Heisenberg

1925 - 1927

Proposed that electron paths cannot be predicted.