History of the Atom

Democritus

460

Developed the idea of atoms in 460 B.C.
If you break a piece of matter in have again and again how far will you get until you can’t get any further
He thought that it had to end at some point at the smallest possible bit of matter.

John Dalton

Jan 1, 1803

English Chemist, Performed experiments with various chemicals (1800s) that showed matter consists of lumpy particlesDidn’t know about their structure.

J.J. Thomson

Sep 23, 1897

Discovered the electron in 1897. Proposed the ‘Raisin in the Pudding’ model.

Albert Einstein

Jan 1, 1905

Published the famous equation E = MC2 (1905)

Ernest Rutherford

Jan 1, 1911

Conducted an experiment to investigate the inside of the atom.

Robert Millikan

Jan 1, 1915

Oil drop experiment determined the mass of an electron.
Proved Einstein’s formula correct

Niels Borh

Jan 1, 1922

Danish physicist.
Came up with a theory that said the electrons do not spiral into the nucleus and came up with some rules for what does happen.
Rule 1: Electrons can orbit only at certain allowed distances from the nucleus
Rule 2: Atoms radiate energy when an electron jumps from a higher-energy orbit to a lower-energy orbit. An atom absorbs energy when an electron gets boosted from a low-energy orbit to a high-energy orbit

Louis de Broglie

Jan 1, 1924

Thought about particles of matter
He thought that if light can exist as both particles and waves, why couldn’t atom particles also behave like waves?

Wolfgang Pauli

Jan 1, 1924

Austrian physicistPredicted that an electron should spin while it orbits around the nucleus. (1924)Gave a rule governing the behavior of electrons within the atom that agreed with the experiment (Pauli’s exclusion principle)

Werner Heisenberg

Jan 1, 1925

German physicist. Matrix mechanics theory which explained the behavior of atoms based on mathematical quantities.

Erwin Schrödinger

Jan 1, 1926

Austrian physicistAtom as a wave model (1926)psi symbol from the Greek alphabet