Atomic Timeline by Albert Saunders

Main

Democritus (Greek Philosopher)

460 BC - 370 BC

First suggested atomic existence. Believed atoms were indivisible and indestructible.

John Dalton (English Chemist + Teacher)

1766 - 1844

Studied element ratios in chemical reactions. Created "Dalton's Atomic Theory".

Eugen Goldstein

1886

Discovered protons through cathode ray experiment.

JJ Thomson (English Physicist)

1897

Discovered the electron. Passed electric current through low pressure gas to identify electrodes, which led to electrons.

Hantaro Nagaoka (Japanese Physicist)

1904

Suggested atoms have nucleus, electrons revolve like saturn's rays.

Ernest Rutherford (English Physicist)

1911

Discovered and named the nucleus and nuclear atom. Concluded that electrons are distributed around the nucleus.

Niels Bohr (Danish Physicist)

1913

Believed electrons move at fixed distances from the nucleus. Their energy levels determine their distance form the nucleus.

Robert A Millikan (US Physicist)

1916

Experimented to find electron properties. Concluded that an electron has a charge of -1 and is 1/1840 of a hydrogen atom.

Louis de Broglie (French Physicist)

1923

Believed electrons move like waves.

Erwin Schrodinger

1926

Developed mathematical equations to describe electron motions. Produced the electron cloud model.

James Chadwick (English Physicist)

1932

Discovered neutrons. Also discovered quarks, particles that form neutrons and protons.