A) how many sub-shells are associated with n = 4? (b) how many electrons will be present in the sub-shells having ms value of �1/2 for n = 4?

For a given value of ‘n’, ‘l’ can have values from zero to (n – 1).

ie, 0,1,2,3

Four sub-shells are associated with n = 4, which are s, p, d and f.

b) For n=4

the no of orbitals will be(n^2) that is 16

2 electrons will go to each orbital with spins -1/2 and +1/2

therefore no of electrons having spin -1/2 will be 16