Atomic Structure Timeline

Idea of the Atom

100

It was discovered by Democritus In 440 BC but the website won't let me set it to 440 BC

Daltons atomic theory

Sep 6, 1803

Dalton theory on the Atom

Discovery of Electrons

Dec 11, 1897

Experiments by J.J. Thomson in 1897 led to the discovery of a fundamental building block of matter

Discovery of the nucleus in an Atom

Jan 1, 1911

The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. Discovered by Ernest Rutherford

Discovery of Protons

Jan 1, 1920

Shortly after the World War I, in 1920, Rutherford proposed the name proton for the positively charged particles in the nucleus of an atom

Electron orbitals, shells and clouds

Jan 1, 1922

Niels Bohr described atomic structure and the presence of orbital shells. The atomic model consisted of successive shells, in which the electrons were arranged

Discovery of Neutrons

Jan 1, 1932

It is remarkable that the neutron was not discovered until 1932 when James Chadwick used scattering data to calculate the mass of this neutral particle