Question

How many 1s energy states are present in one mole of sodium vapour? Are they all filled in normal conditions? How many 3s energy states are present in one mole of sodium vapour? Are they all filled in normal conditions?

Answer 1

For sodium, the atomic number is 11. The electronic configuration of sodium is 1s² 2s² 2p⁶ 3s¹.
One sodium atom has 11 electrons. Thus, if the sodium crystals consist of N atoms, the total number of electrons will be 11 N. We know that for each atom, there are two states in the energy level 1s. Thus, the sodium crystal will have 2 N states for 1s energy level. Similarly, the number of states in 3s energy level will also be 2 N. 1s state is filled under normal condition. But the 3s state has only one electron per sodium atom, so the 3s band will be half-filled.