History of the Atom

Events

Demoritus

400 bc

His contribution stated that everything is composed of "atoms" And thy are physically, but not geometrically, indivisible. He believed all four elements were made out of matter.

Dalton

1803

Proposed the idea that elements are extremely small partials called atom. Also that atoms of a given element are identical in size, mas and other properties. They are indivisible and indestructible.

Thomson

1897

Thomson discovered electrons using a Crooke or cathode ray tube. He made a new model and named it the plum pudding model. Each atom was a sphere filled with positively charged fluid, and negatively charged electron.

Rutherford

1908 - 1913

Rutherford performed the gold foil experiment. From this experiment he discovered a nucleus. This showed scientist that atoms were more than just empty space with scattered neutrons and that atoms must have a positive charged center that contains most of its mass.

Bohr

1913

The Bohr model is also known as the Planetary mode because of its similarities to our solar system.

Modern Atomic Theory

1962

This new model is also known as the Schrodinger and Heisenbeg model. This is deference from the Bohr model because the electrons do not circle the nucleus the same way.