According to this principle in the ground state of the atoms the orbital’s are filled in order of their increasing energies means electrons enter higher energy orbital’s so order in which orbital’s are filled is 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p.
Pauli Exclusion Principle
Hund’s Rule of Maximum Multiplicity
· Does not take place until each orbital belonging to that sub-shell has got one electron each i.e. it is singly occupied.