The subshell in which the last electron of the element is filled up is the block of the element. Therefore from the subshell electronic configuration ,the block, group number and period number can be found out. But the method to be adopted is different in the case of group number of s,p,d blocks.

In the s block elements, the number of electrons in the outermost s subshell will be the group number.

The group number of p block elements can be obtained by adding 10 to the total number of electrons in the s and p subshells of the outermost shell or by adding 12 to the number of p shell electrons in the outermost shell.

Group number of d block element is found out by adding s-subshell electrons of the outermost shell and electrons in the preceding inner d subshell together.