Nevertheless, in spite of Rutherford's estimation that gold had a central charge of about 100 (but was element Z = 79 on the periodic table), a month after Rutherford's paper appeared, Antonius van den Broek first formally suggested that the central charge and number of electrons in an atom was exactly equal to its place in the periodic table (also known as element number, atomic number, and symbolized Z).
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In his 1891 novel The Doings of Raffles Haw, Arthur Conan Doyle talks about turning elements into other elements of decreasing atomic number, until a gray matter is reached.
It was not until the work of Henry Moseley working with the Bohr model of the atom with the explicit idea of testing van den Broek's theory, that it was realized that atomic number was indeed a purely physical property (the charge of the nucleus) which could be measured, and that van den Broek's original guess had been correct, or very close to correct.
In 1913 Henry Moseley found an empirical relationship between the strongest X-ray line emitted by atoms under electron bombardment (then known as the K-alpha line), and their atomic number Z. Moseley's empiric formula was found to be derivable from Rydberg and Bohr's formula (Moseley actually mentions only Ernest Rutherford and Antonius Van den Broek in terms of models).
Neutronium, sometimes referred to as an "element" with atomic number 0
Boron, the (modern) element with atomic number 5 on the periodic table
In 1914, a year before he was killed in action at Gallipoli, the English physicist Henry Moseley found a relationship between the X-ray wavelength of an element and its atomic number.
In 1902, Bohuslav Brauner suggested there was an element with properties intermediate between those of the known elements neodymium (60) and samarium (62); this was confirmed in 1914 by Henry Moseley who, having measured the atomic numbers of all the elements then known, found there was no element with atomic number 61.
Technetium, a chemical element with atomic number 43 and symbol Tc.
Ununennium, an unsynthesized chemical element with atomic number 119.
Zq, the Molecular Hamiltonian charge of a nucleus: atomic number Z * q (electrons' negative elementary charge)