Atomic Theory Timeline

Demitrious comes up with the atom.

440

Demitrious came up with the atom in 440B.C. He said that if you kept cutting a peice of silver in half then you would end up with an uncuttable peice called an atom. He said atoms were small hard particles that form different shapes and materials by joining together.

John Dalton

Apr 25, 1700

In the late 1700s a chemist named John Dalton made a major revision to the atomic theory. He had three main parts. He said all substances are made of atoms, atoms of the same element are exactly identical, and atoms join with other atoms to make new substances.

JJ Thompson

Apr 25, 1897

Thomson knew atoms had no overall charge so he tested this with a negetive partice beam these negetive particles were know as electron. He created the plum pudding model.

Ernest Rutherford

Apr 25, 1909

Rutherford proposed the idea of the nucleus which is a small dense peice in the center of the atom. He also said that the nucleus ws 100,000 times smaller than the entire atom.

Neils Bohr

Apr 25, 1913

Neils Bohr discovered that electrons travel in a definate path around the atom but can jump from one path to another.

Modern

Apr 25, 2000

Many Modern scientists discovered that there is no definate path that electrons take but they are likely to be in a region at a timwe.