Atomic Theory

Events

Democratis

Approx. 460 BC - Approx. 370 BC

He believed that the world is an empty space in which atoms moved around. He also believed that changes in matter are only possible because the atoms are being rearranged.

Aristotle

Approx. 367 BC - Approx. 347 BC

Aristotole did not support the Atomic Theory, that all matter is made up of atoms, but rather proposed that everything was made up of the four elements, Earht, Fire, Water, and Air.

Evangelista Torricelli

1608 - 1647

He discovered that air has weight and can cause pressure. He found this out when he created the "Barometer" .

Antoine Lavoisier

1743 - 1794

He proposed the Law of Conservation of Matter/Mass, meaning that mass cannot be destroyed, only changed.

John Dalton

1766 - 1844

Confirmed Democratis' theory that all matter consists of tiny particles. He also theorized that atoms are indestructible and unchangeable, which is untrue. He said that atoms of the same elements are identical, this was later corrected to "Elements are characterized by their atomic number.". He also discovered chemical change in atoms.

J.J Thomson

1856 - 1940

He experimented with the "Cathode Ray Tube" through which he discovered the electron, and couldn't find any positive in the atoms (for a while). He described the atom like "Plum Pudding"; a bunch of positive stuff with electrons able to be removed.

Ernest Rutherford

1871 - 1937

He used uranium to produce alpha particles. He theorized that the atom was mostly empty space with a positive center (Nucleus).

Niels Bohr

1885 - 1962

He discovered the "Electron Cloud", and the stages of an atom.

Louis DeBroglie

1892 - 1987

He discovered that all matter has wave properties.