Q.
Which of the following are isoelectronic species?
(i) $NH _{3}$
(ii) $CH _{3}^{+}$
(ii) $NH _{2}^{-}$
(iv) $NH _{4}^{+}$
Choose the correct answer from the codes given below.
Solution:
Species
Number of electrons
(i)
$NH _{3}$
$7+1 \times 3=10$
(ii)
$CH _{3}^{+}$
$6+1 \times 3-1=8$
(iii)
$NH _{2}^{-}$
$7+1 \times 2+1=10$
(iv)
$NH _{4}^{+}$
$7+1 \times 4-1=10$
Since $(i), (iii)$ and $(iv)$ contain equal number of electrons, so these are called isoelectronic species.
(A positive charge means loss of an electron and a negative change means gain of an electron).
| Species | Number of electrons | |
|---|---|---|
| (i) | $NH _{3}$ | $7+1 \times 3=10$ |
| (ii) | $CH _{3}^{+}$ | $6+1 \times 3-1=8$ |
| (iii) | $NH _{2}^{-}$ | $7+1 \times 2+1=10$ |
| (iv) | $NH _{4}^{+}$ | $7+1 \times 4-1=10$ |