Question

Two electrons occupying the same orbital are distinguished by
a) azimuthal quantum number
b) spin quantum number
c) magnetic quantum number
d) orbital quantum number

Answer 1

Correct Answer (b) ⇒ Spin quantum number 

So it is clear that 2 electrons occupying the same orbital are distinguished by Spin quantum number.

 Reason / Explanation :-


For spin Quantum number it has two values +1/2 or -1/2 ,
Hence the value of n, l ,m are same for the two electrons occupying in the same orbitals, but only the $m_{s}$  is different , which is $m_{s} = +1/2 , -1/2$ 


⇒ Spin quantum number explains the direction through which the electron spins in an orbital. so obviously there are only 2 possible directions . which is either clockwise or anticlockwise. 

⇒ So Two electron which are available in the same orbitals , must have opposite spins . Hence spin quantum number distinguished b/w the two electrons.



Hope it Helps :-)

Answer 2

The correct answer is Spin quantum number