Atomic Theory Timeline



440 BCE

Democritus was Greek and born in 460 BCE, he died 370 BC. His theory stated that atoms are indivisible and indestructible. He discovered atoms.

Antoine Lavoisier

Approx. 1778

Lavoisier was a French chemist. He found and named both oxygen and hydrogen. He discovered the Law of Conservation of Mass.

John Dalton


Dalton was an English scientist. He came up with the modern atomic theory and listed five rules to it.

J.J. Thomson


Thomson was an English physicict. He discovered negatively charged electrons in his cathode ray experiment. He came up with the "plum pudding" model.

Marie Curie


Curie was a Polish physicist and chemist. She discovered the two elements, polonium and radium. She created the radioactivity field with these two elements.

Max Planck


Planck was a German physicist. He came up with the quantum theory. It was a solution for finding the form of a spectrum in physics.

Albert Einstein


Einstein was a German-born physicist. He came up with with the theory of relativity basing his work off Planck's quantum theory.

Robert Millikan


Millikan was an American physicist. He figured out the unit charge of an electron in his oil drop experiment, which eventually led to figuring out the mass of an electron and proton.

Ernest Rutherford


Rutherford was a New Zealand-born British physicist. He discovered the nuclear atom after doing his gold-foil experiment. He is also known as the "father of nuclear physics".

Niels Bohr


Bohr was a Danish physicist. He discovered in hydrogen atoms that orbiting electrons surround the nucleus. This discovery was based off of Planck's quantum theory and he also improved Planck's theory.

Louis de Broglie

Approx. 1924

Broglie was a French physicist. He contributed to the quantum theory by stating that electron particles can have waves because waves have particles.

Erwin Schrödinger


Schrödinger was an Austrian physicist. He came up with some more reasoning for the quantum theory. He also came up with the wave equation basing it off Broglie's work.

Werner Heisenberg


Heisenberg was a German physicist. He came up with his uncertainty principle which states it is impossible to know the position and velocity of an electron at the same time.

James Chadwick


Chadwick was an English physicist. He discovered the neutron, which has a neutral charge. This discovery led to the understanding of fission and the creation of atomic bombs.