The Evolution of the Atomic Model

Democritus

430 BCE

Democritus believed that all matter could be divided until you reached an indivisible particle. He called these 'atomos', or atoms. He did not support his claim with any experiments.

John Dalton

1803

John Dalton created the atomic theory. The theory was that all matter was made up of atoms, atoms are the smallest particles of matter, atoms are unique based on the type of matter, and atoms are indestructible.

J.J Thomson

1897

Thomson used cathode rays to find out that the 'rays' were not really rays and that they were negatively charged particles. We call these electrons today. Using this he developed the Plum Pudding model, which has electrons scattered randomly in the atom, like fruit scattered in a plum pudding.

Ernest Rutherford

1911

Ernest Rutherford is famous for conducting the gold foil experiment. With this, he concluded three main statements. 1. The atom is mostly empty space. 2. The nucleus is positively charged. 3. The nucleus carries most of the atom's mass.

Niels Bohr

1913

Niels Bohr improved Rutherford's model. He said that the electrons move in circular orbits around the nucleus, and each orbit has a different amount of energy,

Erwin Schrodinger

1926

Schrodinger hypothesized that the electrons did not move in orbit but they existed in a cloud of electrons, and we could only predict the chances of an electron being in a certain place. This is the model that most scientists use today, as it is the most accurate that our technology can provide.