Foundations of the Atom

around 300 B.C. Aristotle attempted to prove that all matter was made from the four elements

300

This caused Democritus' theory to be over looked for 2,000 years

460 B.C the Greek philosopher, Democritus, develops the idea of atoms.

460

Antoine Lavoisier's experiments and discovery led to his theory of the Law of Conservation of Mass

Dec 1, 1789

Much of his experiments led to the atomic theory.

Joseph Proust proposed the the Law of Definite Proportions

Dec 1, 1799

These law stated that in any given chemical compound, the elements always combine in the same proportion with each other.

John Dalton discovers the atom

Nov 21, 1800

John Dalton discovers the Law of Multiple Proportions

Nov 20, 1803

John Dalton writes "A New System of Chemical Philosophy"

Nov 21, 1808

J. J. Thomson's discovery of the electron.

Dec 3, 1897

Niels Bohr refined the nuclear model

Dec 3, 1913

Ernest Rutherford proposes the nuclear model of the atom

Dec 3, 1919

James Chadwick discovered the nuetron

Dec 4, 1920

contemporary theories led the the Modern Atomic Theory

Dec 4, 1950