Atomic History

Democritus

Proposed the theory that all mater is made of tiny, indivisible particles that vary in shape and size and move at random. (Sphere)

John Dalton

Imagined atoms as solid and impenetrable, introduced the modern element systems later used in the modern periodic table

JJ Thompson

Proved that atoms are divisible and proposed the “plum pudding” or “chocolate chip cookie” model, positive matter with protons and electrons— no neutrons.

Ernest Rutherford

Realized that electrons go around the nucleus, which is filled with neutrons and protons. Proved that atoms are not solid spheres but actually mostly empty space with the gold foil experiment.

Niels Bohr

Proposed a model with electrons in rings traveling around the nucleus (protons + neutrons) in a sort of solar system formation

Werner Heisenberg

Discovered the uncertainty principle— we can’t know the position or momentum of an electron exactly.

James Chadwick

Discovered the neutron by bombarding Beryllium with alpha particles

Erwin Schrödinger

Theorized that the behavior of electrons with atoms could be explained by treating them mathematically as matter waves. Predicted where an electron MIGHT be found. Electron cloud model.

Louis de Broglie

Electrons can move like a wave. Light can act as a particle and a wave.