Henry Gwyn Jeffreys Moseley was an English physicist, whose contribution to the science of physics was the justification from physical laws of the previous empirical and chemical concept of the atomic number. This stemmed from his development of Moseley's law in X-ray spectra.
Moseley in 1914
Moseley in the Balliol-Trinity Laboratories in 1910
Blue plaque erected by the Royal Society of Chemistry on the Townsend Building of Oxford's Clarendon Laboratory, commemorating Moseley's work on X-rays emitted by elements
The atomic number or nuclear charge number of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei composed of protons and neutrons, this is equal to the proton number (np) or the number of protons found in the nucleus of every atom of that element. The atomic number can be used to uniquely identify ordinary chemical elements. In an ordinary uncharged atom, the atomic number is also equal to the number of electrons.
Russian chemist Dmitri Mendeleev, creator of the periodic table.
Niels Bohr, creator of the Bohr model.
Henry Moseley in his lab.