Moseley, Henry Gwyn-Jeffreys (1887-1915), an English physicist. Moseley studied the X rays that an atom emits when it is bombarded by electrons. He discovered that there exists a relationship between the wavelengths of the X rays emitted by atoms of a particular chemical element and the element's atomic number. The discovery showed that atomic number is indicative of fundamental properties of a chemical element and helped establish atomic number in place of atomic weight as the basis of the periodic classification of the chemical elements. Moseley was born at Weymouth, and attended Eton and Oxford. He was a lecturer and did research under Ernest Rutherford. Moseley was killed in World War I.