Model of the Atom Timeline

Maggie Lou Geiger

1803 - John Dalton

John Dalton pictures atoms as tiny, indestructible particles, with no internal structure.

1897 - J.J. Thomson

J.J. Thomson, a British scientist, discovers the electron, leading to his "plum-pudding" model. He pictures electrons embedded in a sphere of positive electric charge.

1904 - Hantaro Nagaoka

Hantaro Nagaoka, a Japanese physicist, suggests that an atom has a central nucleus. Electrons move in orbits like the rings around Saturn.

1911 - Ernest Rutherford

New Zealander Ernest Rutherford states that an atom has a dense, positively charged nucleus. Electrons move randomly in the space around the nucleus.

1913 - Niels Bohr

In Niels Bohr's model, the electrons move in spherical orbits at fixed distances from the nucleus.

1924 - Louis de Broglie

Frenchman Louis de Broglie proposes that moving particles like electrons have some properties of waves. Within a few years, evidence is collected to support this idea.

1926 - Erwin Schrödinger

Erwin Schrödinger develops mathematical equations to describe the motion of electrons in atoms. His work leads to the electron cloud model.

1932 - James Chadwick

James Chadwick, a British physicist, confirms the existence of neutrons, which have no charge. Atomic nuclei contain neutrons and positively charged protons.