Atomic Theory

Events

Democritus

400 B.C.

He was the first person to use the word atom. He found that all matter consists of atoms. Atoms are completely solid.

Dalton

1803

He discovered that all matter consists of tiny particles called atoms. These atoms are indestructible and unchangeable. He also sorted elements by their weight. He believed that atoms couldn't be divided and that atoms of the same element would have the exact same mass and densities. This was later proven to be false.

Thomson

1897

He discovered the electron using a cathode ray tube. He also found that each atom is filled with positively charged "fluid", and that negatively charged particles float in that "fluid".

Rutherford

1911

He performed the Gold Foil Experiment, and discovered the nucleus and that electrons orbit the nucleus.

Bohr

1913

He took Rutherford's model and was able to perfect and make that model even better. He was the one who renamed the model the Planetary Model. because the electrons orbited like the planets around the sun. It is a one dimensional model.

Modern Atomic Theory

1926

This was discovered by Schrodinger and Heisenberg and named after them. Another name for this model is the Electron Cloud Model. This is a three dimensional model.