Chemical Bonding Result Question 12
12. In which of the following pairs of molecules/ions both the species are not likely to exist?
(2013 Main)
(a) $\mathrm{H}_2^{+}, \mathrm{He}_2^{2-}$
(b) $\mathrm{H}_2^{-}, \mathrm{He}_2^{2-}$
(c) $\mathrm{H}_2^{2+}, \mathrm{He}_2$
(d) $\mathrm{H}_2^{-}, \mathrm{He}_2^{2+}$
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Answer:
Correct Answer: 12. ( c )
Solution:
- Species having zero or negative bond order do not exist.
$\mathrm{H}_2^{2+}(1+1-2=0)=\sigma l s^0$
Bond order $=0$
$\mathrm{He}_2(2+2=4)=\sigma 1 s^2, \stackrel{*}{\sigma} 1 s^2$
$\text { Bond order }=\frac{N_b-N_a}{2}=\frac{2-2}{2}=0$
So, both $\mathrm{H}_2^{2+}$ and $\mathrm{He}_2$ do not exist.
BETA
