Periodic Classification of elements

Electronic configuration of atoms depends on two things:

1)Capacity of shell which is given by 2 n² . For eg. for first shell it is 2(1)² =2, for 2nd it is 8, for 3rd 18 and so on.

2)It depends on the order in which it gets filled in subshells(s,p,d,f) of the shells. Theses subshells have varied capabilities and electron's get filled in them in accordance with aufbau's and hund's multiplicity rule. Thus we can obtain configuration of any element.

So various configurations are obtained following above rules.