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Henry Moseley X-Ray Imaging Facility - Henry G J Moseley


Henry Moseley
Henry G J Moseley

Henry "Harry" Gwyn Jeffreys Moseley was born in Weymouth in 1887, the son and grandson of eminent scientists. He went to Eton and subsequently read physics at Trinity College, Oxford. After graduating in 1910 he secured a position as a demonstrator at the University of Manchester with Ernest Rutherford where he used the characteristic spectra of X-rays obtained by diffraction in crystals to determine a systematic relation between emitted wavelength and atomic number and was thus able to derive Moseley's Law. Previously, elements had been assigned their positions within the Periodic Table on the basis of their chemical properties but Moseley showed that the elements could be arranged with certainty according to their atomic number. The Bohr model of the Rutherford nuclear atom where the element's atomic number was equal to the positive nuclear charge was thus confirmed. Using his method Moseley was also able to predict the existence of several undiscovered elements and their spectral patterns in gaps within the Table.

In 1914 Moseley resigned from Manchester with the intention of taking up a chair at Oxford, but when war broke out he turned down the job offer and volunteered for service in the Royal Engineers where he became a brigade signal officer with the rank of second lieutenant. He was posted to Gallipoli where in the battle of Sari Bair in August 1915 he was shot through the head by a sniper whilst telephoning an order. It has been suggested that Moseley's death was an impetus for the policy which was subsequently adopted of the government not allowing scientists to be recruited for combat service. It was also speculated that had he lived, his work would have earned him a Nobel Prize.

Many years later, in 1962, Niels Bohr said of Moseley, "You see actually the Rutherford work [the concept of the nuclear atom] was not taken seriously. We cannot understand today, but it was not taken seriously at all. There was no mention of it any place. The great change came from Moseley." de Broglie said that Moseley's Law was "one of the greatest advances yet made in natural philosophy".