#"Atomic number"#, #Z#, is specified by the by the number of nuclear protons. For #Z=1# we have the element #"hydrogen"#; #Z=2#, #"helium"#; ...........#Z=23#, we have the element #"vanadium"#............
The #"Noble gases"# have #Z=2, 10, 18,36# etc. And these numbers reflect electronic structure as well as nuclear structure. The moral? ANY two different elements have different values of #Z#.