The History of the Atom

Democritus 460 B.C.

460

-Originated the concept of the Atom.
-Did not perform any experiaments
-His ideas were based on theory since no experiament was conducted

John Dalton

Jan 1, 1766

-Father of the atomic theory
-1) All matter is made of atoms. Atoms are indivisible and indestructible. 2) All atoms of a given element are identical in mass and properties 3) Compounds are formed by a combination of two or more different kinds of atoms. 4) A chemical reaction is a rearrangement of atoms.

J,J Thompson

Jan 1, 1897

-Studied canal rays and found that they were connected with protons
-Announced that cathode rays were negatively charged particles now called electrons.
--Plum pudding model, believed electrons were like plums.

Robert Milikan

Jan 1, 1909

-Began experiments to determine the electric charge of electrons.
-Performed oil drop experament.
-1916 he determined the mas of electrons

Ernest Rutherford

Jan 1, 1911

-Helped develop nuclear atomic model of the atom
-Worked with J.J Thompson
-He did the gold foil experament and discovered the nucleus.
- Renamed canal rays to protons in 1920

Niels Bohr

Jan 1, 1922

-Liquid Droplet theory, understanding of the mechanism of nuclear fission

Erwin Schrodinger

Jan 1, 1930

-Looked at electrons as continuous clouds.
-Introduced "Wave mechanics" as a different model of the atom
-Developed the probability function for the hydrogen atom

James Chadewick

Jan 1, 1932

-Using alpha particles, he introduced a neutral atomic particle with the mass that is similar to a proton.
-Discovered neutron
-worked with rutherford