Contributors to the Atomic Theory

Democritus

400 BCE

He was an ancient greek philosopher-- his contribution to science was the "Atomic Theory".
He came up with this theory about 2400 years ago.

John Dalton | Discovery of atoms in matter

1803

Dalton was born on September 26, 1776 in Eaglesfield, Columbia, UK.
His contribution was that all is matter is composed of atoms, invisible, and indestructible.
Dalton stated that atoms cannot be subdivided, created, or destroyed.

J.J. Thomson | Discovery of the Electron

1897

Thomson was born on December 18, 1856 in Cheetham Hill, Manchester, UK.
He discovered the electron in 1897. His experiment to his discovery was with a cathode ray, tube-- it was used for negative charges.
Thomson view on the atom was composed of electrons and his structure only concluded negative electrons.

Ernest Rutherford | Discovery of the Nucleus

1911

Ernest Rutherford was born August 30. 1871 in Brightwater, New Zealand.
The Gold Foil experiment led him to propose the concept of the nucleus in an atom. The structure had the atom consisting a tiny positive mass surrounded by a cloud of negative electrons.

Niels Bohr | Quantum Theory

1913

Neils Bohr was born on October 7, 1885 in Copenhagen, Denmark-- his contribution was based on the hydrogen atom-- electrons should move around the nucleus but only in prescribed orbits.

James Chadwick | Discovery of the Neutron

1932

James Chadwick was born October 20. 1891 Bollington, UK.
His contribution to the atom was discovering its neutrons, which are located in the center of an atom.
His experiment bombarded beryllium with alpha which released an unknown radiation that in turn ejected protons nuclei.