History of the Atom

Aristotle

400

Aristotle did not believe in the Atomic Theory. He believed that everything was made up from ffire, air, earth, and water. this model was adapted in 400 B.C. It

Democritus

450

Thought to have developed the first Atomic theory. Said you could eventually get the the smallest piece of matter

Antoine Lavoisier

Oct 1, 1783

Discovered Hydrogen and Oxygen. Discpvered the role Oxygen plays in combustion.

John Dalton

Sep 1, 1802

Developed the Atomic Theory.

Henri Becquerel

Feb 24, 1896

Henri Becquerel discovered radioactivity. This produced a charecteristic of elements on the peridoic table.

Marie & Pierre Curie

Dec 26, 1898

Together they discovered Polonium and Radium, Marie coined the term "Radioactivity".

Max Planck

Oct 1, 1900

Planck developed the Quantum Theory.

J.J. Thomson

Oct 1, 1904

Thomson discovered the electron by studying the electric discharge in a high-vacuum cathode-ray tube,

Robert Millikan

Sep 29, 1908

Discovered the charge of the electron. Used the oil-drop apparatus to measure oil droplets suspended by gravity.

Henry Mosely

Oct 1, 1911

Studied under Ernest Rutherford. Established Atomic numbers and improved the periodic table.

Niels Bohr

Sep 1, 1913

Niels Bohr created the Bohr model. It stated that electrons orbit around a nucleus in energy leverls. He perfected Ernest Rutherford's model.

Ernest Rutherford

Oct 1, 1919

Rutherford studied inder J.J. Thomson. He conducted the Gold foil experiment in which he transmuted one element into another.

Werner Heisenberg

Oct 1, 1925

He discovered the allotropic forms of Hydrogen. It was based on the radiation emitted by an Atom.

Erwin Shrodinger

Oct 1, 1926

He developed an equation to find the energy level of an atom.

James Chadwick

Sep 1, 1932

James Chadwick discovered the Nuetron. He studied under Ernest Rutherford. He also established the atomic number. Added the Nuetron to the Atomic model and theory.