Q. Which of the following arrangements shows the correct order of decreasing number of unpaired electrons.
Classification of Elements and Periodicity in Properties
Solution:
Element
Electronic configuration
Number of unpaired electrons
$N$
$1 s^{2} 2 s^{2} 2 p^{3}$
3
$O$
$1 s^{2} 2 s^{2} 2 p^{4}$
2
$Al$
$[ Ne ] 3 s^{2} 3 p^{1}$
1
$Ca$
$[ Ar ] 4 s^{2}$
0
| Element | Electronic configuration | Number of unpaired electrons |
|---|---|---|
| $N$ | $1 s^{2} 2 s^{2} 2 p^{3}$ | 3 |
| $O$ | $1 s^{2} 2 s^{2} 2 p^{4}$ | 2 |
| $Al$ | $[ Ne ] 3 s^{2} 3 p^{1}$ | 1 |
| $Ca$ | $[ Ar ] 4 s^{2}$ | 0 |