COntribution
Chadwick discovered neutrons.They differed from alpha rays because they repelled considerable electrical forces that are in the nucleus of many heavy atoms. A neutron can then penetrate and split the nuclei of most elements.
Significance of COntribution
This advancement allowed for the fission of uranium, and the creation of very powerful bombs.
Fun Fact
He was a prisoner of war from 1913-1918 in Germany.