Atomic Theory

Events

Democritus

460 BC

He believed matter was composed of fundamentally invisible particles called atomos.

John Dalton

1803

He said an atom can be further subdivided into protons, neutrons, and electrons. He also said an atom is the smallest particle that takes part in chemical reactions.

JJ Thomson

1856

He concluded that atoms are made of positive cores and negatively charged particles within it.

Ernest Rutherford

1911

He said atoms have a small charged nucleus surrounded by largely empty space, and circled by tiny electrons.

Niels Bohr

1913

He made a model that shows the atom as a small, positively charged nucleus surrounded by orbiting electrons.

Erwin Schrodinger

1926

He created an equation that helps explain the movement of the electrons.