B.They all have their valence electrons in the same type of subshell
Explanation:
The electron configurations of elements in the same group (column) of the periodic table have them in the same type of subshell.
But the subshells may be of different shells. Thus , the energies of them need not be the same.
For example , The Alkalai Metals are found in the first column of the periodic table Group IA. This set of elements all have valence electrons in only the '' orbital and because they are in the first column they all have configuration. i.e,