Which combinations of n and l represent real orbitals, and which do not exist a) 2s b) 3p c) 5s d) 1d

Answer : The combinations of n and l don not exist is, (d) 1d

Explanation :

Principle Quantum Numbers : It describes the size of the orbital and the energy level. It is represented by n. Where, n = 1,2,3,4

Azimuthal Quantum Number : It describes the shape of the orbital. It is represented as 'l'. The value of l ranges from 0 to (n-1). For l = 0,1,2,3... the orbitals are s, p, d, f...

(a) For 2s :  

n=2 and l can have value 0 to (n-1) i.e. 0 and 1 only. For s, l=0 which is possible.

(b) For 3p :  

n=3 and l can have value 0 to (n-1) i.e. 0, 1 and 2 only. For p, l=1 which is possible.

(c) For 5s :  

n=1 and l can have value 0 to (n-1) i.e. 0, 1, 2, 3 and 4 only. For s, l=0 which is possible.

(d) For 1d :  

n=1 and l can have value 0 to (n-1) i.e. 0 only. For d, l=2 which is not possible.

Hence, the combinations of n and l don not exist is, (d) 1d