The "plum-pudding" is disproved by the gold foil experiment by Ernest Rutherford, when he discovered the nucleus of the atom. Marie Curie receives a second Nobel Prize, this time in Chemistry, for the isolation of radium and polonium and for her investigation of their chemical properties.
Niels Bohr publishes theory of atomic structure, combining nuclear theory with quantum theory.
Albert Einstein publishes the general theory of relativity. The theory proposes that gravity, as well as motion, can affect the intervals of time and of space.
June - Rutherford bombards nitrogen gas with alpha particles and obtains atoms of an oxygen isotope and protons. This transmutation of nitrogen into oxygen was the first artificially induced nuclear reaction.