### Q.67:- (a) How many sub-shells are associated with n = 4 ? (b) How many electrons will be present in the sub-shells having m_{s }value of –1/2 for n = 4 ?

**Answer:-**

(a) n=4, *l *= 0, 1, 2, 3. 4 sub-shells are associated with n = 4

(b) No. of orbitals in the shells = n^{2 }= 4^{2 }= 16

Each orbitals has one electron with m_{s }= -1/2. Hence, there will be 16 electrons with m_{s }= -1/2.