On the basis of quantum numbers, justify that the fourth period of the Modern periodic table should have `18` elements.

Explanation

The sixth period of the periodic table begins with n=6.It involves the filling of 6s, 4f, 5d and 6p subshell in the increasing order of energy. The total number of orbitals available are 16 and therefore, the maximum number of electrons that can be accommodated is 32. Thus, the sixth period of the periodic table should have 32 elements.