1887-1915
English physicist. Trinity College, Oxford, 1910. He began his research under Ernest Rutherford while serving as lecturer at the Univ. of Manchester and soon devoted himself entirely to research. Extending the work of Max von Laue and of W. H. Bragg and W. L. Bragg on the X-ray spectra of elements, Moseley made systematic studies of the relation between the bright-line spectra of different elements. He found that the frequency of vibration of the X rays emitted by each element when bombarded with cathode rays bore a simple relationship to whole ordinal numbers. These ordinal numbers are the atomic numbers; Moseley concluded that the atomic number is equal to the charge on the nucleus. When the elements are arranged according to their atomic numbers the sequence, although almost the same as Mendeleev's arrangement in order of increasing atomic weight, differs slightly; these differences account for the few discrepancies inherent in the Mendeleev system. The genius of Moseley's work was widely recognized. He was killed at Gallipoli in World War I.