Question
In a given atom no two electrons can have the same values of all the four quantum numbers. This is called
A.
Hund’s rule
B.
Aufbau principle
C.
Uncertainty principle
D.
Pauli’s exclusion principle
Answer :
Pauli’s exclusion principle
Solution :
According, to Pauli’s exclusion principle “no two electrons in an atom can have the same values of all the four quantum numbers.”
In $$1{s^2}$$
$$\eqalign{
& {\text{for }}I{\text{ electron}}\,\,n = 1,\,l = 0,m = 0,s = + \frac{1}{2} \cr
& {\text{for }}II{\text{ electron}}\,\,n = 1,\,l = 0,m = 0,s = - \frac{1}{2} \cr} $$
It means if the values of $$n, l,$$ and $$m$$ are same, then the value of spin quantum number must be different, i.e. $$ + \frac{1}{2}$$ and $$ - \frac{1}{2}.$$