Moseley, Henry Gwyn Jeffreys (1887-1915)

English physicist. From 1913 to 1914 he devised the series of atomic numbers (reflecting the charges of the nuclei of different elements) that led to the revision of Russian chemist Dmitri Mendeleyev's periodic table of the elements. Moseley was born in Weymouth, Dorset, and studied at Oxford. He worked in the Manchester laboratory of Ernest Rutherford, the pioneer of atomic science, 1910-13, and then at Oxford. Moseley was killed during the Gallipoli campaign of World War I. In 1913 Moseley introduced X-ray spectroscopy and found that the X-ray spectra of the elements were similar but with a deviation that changed regularly through the series. A graph of the square root of the frequency of each radiation against the number representing the element's position in the periodic table gave a straight line. He called this number the atomic number of the element; the equation is known as Moseley's law. When the elements are arranged by atomic number instead of atomic mass, problems appearing in the Mendeleyev version are resolved. The numbering system also enabled Moseley to predict correctly that several more elements would be discovered.