Historical Atomic Theory

John Dalton

Mar 31, 1807

Proposed Billard Ball model atom is a uniform solid sphere.

JJ Thompson

Mar 31, 1903

Proposed ‘Plum Pudding’ model – atom has a positive sphere (pudding) with negative electrons (plums) dispersed throughout.

Ernest Rutherford

Mar 31, 1911

Discovered nucleus of atoms. Proposed ‘Nuclear’ model – atom has dense, positive nucleus surrounded by negative electrons.

Niels Bohr

Mar 31, 1913

Proposed ‘Planetary’ model – atom has electrons that move in circular orbits within specific energy levels.

James Chadwick

Mar 31, 1932

Revised ‘Nuclear’ model – atom has a neutral particles in the nucleus (neutrons).