Model of the Atom Timeline

Payton Pierce

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.