History of Atoms

History of Atoms

Period: 100 to Oct 16, 2000

Democritus

400

400 B.C
He created the first atomic model and named it atomus.

John Dalton

Oct 17, 1803

Proposed an atomic theory with spherical solid atoms based on properties of mass that were measurable.

James Clerk Maxwell

Oct 17, 1873

Proposed electric and magnetic fields filled the void.

J.J. Thomson

Oct 17, 1897

Discovered the charge to mass ratio of of an electron. Also found out that "canal rays" were associated with the proton H +

Robert Millikan

Oct 17, 1909

Determined the charge and mass of an electron.

Ernest Rutherford

Oct 16, 1911

Nucleus was: very dense, very small, and posativley charged. Also assumed that the electrons were located outside of the nucleus.

Niels Bohr

Oct 17, 1922

Developed an explanation of atomic structure that goes with all of the elements on the perodic table.

Werner Heisenberg

Oct 17, 1927

Described atoms by means of formula. Also proposed the Principle of Indeterminancy which states that you can not know both the position and velocity of a particle.

Erwin Schrodinger

Oct 17, 1930

Viewed electrons as a cloud and introduced "wave mechanics" as a mathematical model of the atom.

James Chadwick

Oct 16, 1932

Using alpha particles he discovered a neutral atomic particle. Discovered the neutron.