Discussion Forum



1)

In which of the following pairs of molecules/ions both the species are not likely to exist?


A) $H_{2}^{+},He_{2}^{2-}$

B) $H_{2}^{-},He_{2}^{2-}$

C) $H_{2}^{2+},He_{2}^{}$

D) $H_{2}^{-},He_{2}^{2+}$

Answer:

Option C

Explanation:

Species  having zero or negative bond order do not exist

  $H_{2}^{2+}$ (1+1-2=0)= $\sigma 1s^{0}$

 Bond order =0

 $He_{2}^{}$ (2+2=4)= $\sigma 1s^{2},\sigma^{*}1s^{2}$

 Bond order = $\frac{N_{b}-N_{a}}{2}$

                  =$\frac{2-2}{2}=0$

 so, both  $ H_{2}^{2+}$  and $He_{2}^{}$ do not  exist.