History Of Atom

Democritus

370

Matter is made of small indivisible particles which have different form, position and arrangement. Democritus named these particles atoms.

John Dalton

Oct 29, 1809

Developed an atomic theory stating that spherical atoms had measurable properties of mass

Goldstein

Oct 29, 1886

Used cathode ray tubes to discover that “canal rays” have opposite properties of electron.

J.J Thomson

Oct 29, 1897

Discovers the electron and used cathode ray tubes to determine the charge to mass ratio of an electron to be 1.759 x 10^8 Coulombs/gram.
Found canal rays were associated with a proton, H+.

Ernest Rutherord

Oct 29, 1899

Performed the gold foil experiment to determine that the nucleus is a small, dense, and positively charged part of the atom, based on the assumption that electrons are on the outside of the nucleus. Develops the plum pudding model of the atom.

Robert Millikan

Oct 29, 1909

Performed an oil drop experiment to determine the charge and the mass of an electron to be 1.602 x 10^-19 C and 9.11 x 10^-28 g respectively.

Neils Bohr

Oct 29, 1913

Publishes paper regarding combining nuclear and quantum theories.
Created a model of successive orbital shells based o an equation of fixed radii and quantum numbers.

Erwin Schrodinger

Oct 29, 1925

Saw electrons as a continuous cloud and developed wave mechanics to be a mathematical model for the atom.

James Chadwick

Oct 29, 1932

Discovered neutral atomic particle with similar mass to a proton, the neutron by using alpha particles.