Nuclear Historical Timeline

February 21, 2012

1829

Jons Berzelius discovers a new element, thorium, in samples sent to him by the Reverend Hans Esmark. Thorium will later be found to be somewhat abundant in the Earth’s crust.

1896

Henri Becquerel discovers that pitchblende, an ore containing uranium, causes a photographic plate to darken.

1897

J.J. Thomson discovers the first subatomic particle, the negatively-charged electron. This is the first indication that atoms have internal structure. He later proposes the “plum-pudding” model of the atom, with electrons dispersed in diffuse positive matter. This simplistic model explains why atoms can have no net charge even though they are composed of charged materials.

1898

Marie Curie and G.C.Schmidt independently discovered that thorium and its compounds are radioactive. M. Curie found higher than expected activity in some minerals containing uranium and thorium.

Pierre and Marie Curie isolate polonium and radium from pitchblende. Both are later found to be products from the decay of uranium.