Atomic History

Democritus

Proposed that everything in the world was made up of tiny particles called atomos. His ideas were opposed by popular philosophers of his day.

Aristotle

Believed that all matter was made up of earth, wind, water, and fire. His ideas were believed by the vast majority and many scientists for years.

John Dalton

Supported atomic theory. Believed common substances broke down into the same things. Compounds were combinations of atoms of different elements each of a particular size and mass that could neither be created nor destroyed.

J.J Thomson

Believed the chocolate chip cookie model of the atom. A sphere of positive matter with negative electrons throughout.

Ernest Rutherford

Believed that there was a nucleus where most of the atom’s mass was.

Niels Bohr

Believed the planetary model . The atom had a nucleus and was surrounded by electrons that orbit it at fixed energies and distances.

Werner Heisenberg

Believed the uncertainty principle. It was impossible to show the exact position and speed of electrons as they moved around an atom.