Henri Becquerel was a French physicist who accidentally discovered Radioactivity.

Discovered by Henri Becquerel, also known as Radioactive Decay.

Identified by JJ Thomson, the electron is a subatomic particle, symbol e− or β−, with a negative elementary electric charge.

Other scientists which joined the investigation of radioactivity after Becquerel. Marie discovered source of alpha particles was the radioactive element polonium.

Discovered by Marie and Pierre Curie

Irene, daughter of Marie and Pierre Curie and wife of Frederic Joliot. Worked on natural and artificial radioactivity, transmutation of elements and nuclear physics. Won the Nobel Prize in 1935 with her husband for their synthesis of new radioactive elements.

Investigated the nature of electrical discharges in gases, and invented the Crookes Tube and the Crookes Radiometer.

Bombarded beryllium with alpha particles which created a beam with high penetrating power. This beam mistaken-ed for gamma rays actually led to the discovery of the neutron by James Chadwick

A Crookes Tube is an early experimental electrical discharge tube, with partial vacuum, invented by English physicist William Crookes.