What contribution did Henry Moseley, the scientist shown in the photograph, make to the systematic arrangement of the elements in the periodic table? - Leaving Cert Chemistry - Question 6(b) - 2008

Henry Moseley made a significant contribution to the periodic table by defining the concept of the atomic number. He determined that the atomic number, which is the number of protons in an atom's nucleus, is the characteristic positive charge for each element. His work indicated that elements should be arranged in order of increasing atomic number rather than atomic mass, thereby correcting inconsistencies in the previous arrangement of the periodic table.