Question

Why Moseley changed the basis of classifying elements from atomic weight to atomic number?

Answer 1

Moseley changed the basis of classifying elements from atomic weight to the atomic number because of the following reason-

1. The chemical properties are the function of the valence electron.
2. Elements which have the same valence electrons have similar chemical properties.
3. From atomic number we can get the valence electrons. Hence chemical properties depend on atomic number, not on atomic mass.
4. Therefore, when elements are arranged in order of increasing atomic number, valence electrons of elements repeat after a fixed interval, which leads to the repetition of chemical properties.
5. That's why Moseley changes the basis of classification from atomic weight to atomic number.