Hunds rule states that in a sublevel, each orbital is singly occupied before it is doubly occupied. The electrons present in singly occupied orbitals possess identical spin. Consider the example of Nitrogen. The atomic number is 7. Electronic configuration is 1s2 2s2 2p3. The p orbitals are half-filled. There are three electrons and three p orbitals. This is because the 3 electrons in the 2p subshell will fill all the empty orbitals first before pairing with electrons in them.