Question

 If Nq electrons are contained in the volume at absolute zero temperature, describe how you would count the number of states/orbitals in the system.

Answer 1

According to the Pauli principle, there can only be two electrons in each state, since the spin of the electron takes two values. Accordingly, the number of occupied States will be N/2 if N is even,

or (N-1)/2 + 1 when N is odd.