History Of Atomic Model

Democitus (460-360 BC)

Dec 1, 1700

Theorized that all mater was made up of tiny peices that could not be divided or destroyed.

Spherical Model

Dec 6, 1800

All atoms are spherical shapes and cannot be broken down.John dalton ceated the idea of atomic theory and the spherical atomic model. John dalton also was the first person to link elements to atoms.

Discovering Electrons

Jan 1, 1897

JJ Johnson discovered electrons by using a cathode ray tube. Discovered electrons by proving that cathode rays had a negatively charged particles which he then named Electrons.

Plum Pudding Model

Dec 1, 1897

JJ Johnson theorized that atoms were huge solid positive spheres, filled with negative electrons.

Planetary Model

Jan 1, 1909

Golden Leaf experiment proves that electrons orbit around the nucleus and that the nucleus is positively charged.

Discovery of Necleus

Dec 2, 1911

Rutherford theorized thatthere is a nucleus in an atom and is a small mostly empty space and was dense and postively charged.

Nuclear Model

Jan 1, 1920

Neils Bohr theorized that electrons could only orbit the nucleus in succesively larger orbits around the nucleus. The outer orbits could hold more electrons. The electrons in the outermost shell determine the properties of the atom. Dubbed the "Atomic Model"

Discovery of Neutrons

Jan 1, 1932

James Chadwick discovered neutrons while experimenting with alpha particles. Chadwick said that the atomic mass was not equal to the mass of the atom and that there must be another particle within the necleus of the atom. He used alpha particles to find a the new particle which had the same mass as a proton, but had no charge and was dubbed the "Neutron"