Atomic Numbers and X-ray Spectra

An important breakthrough occurred in 1913 when the brilliant young scientist Henry G. J. Moseley, at the age of 26, discovered the relationship between the atomic number of an element and its X-ray wavelength The square root of the X-ray wavelength is a rectilinear function ofthe atomic number. This opened up a completely new way to iden- 

spectroscopy has an extensive use for qualitative and quantitative analysis of complicated materials and this was so in the history of element discoveries since 1850. 

Moseley was one of several eminent scientists launched by Ernest Rutherford. He was able to show, in a paper of 1913, that X-ray frequencies are correlated to the nuclear charges of elements and thus also to the element s position in the periodic table. Moseley used this relationship to anticipate three new elements with atomic numbers 43, 61 and 75. They were discovered in 1937(technetium), 1945 (promethium) and in 1925 (rhenium). 

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