Question

The bond length of $H _{2}^{+}, H _{2}^{-}$and $H _{2}$ are in the order

• A. $H _{2}{ }^{+} > H _{2} > H _{2}^{-}$
• B. $H _{2}^{-} > H _{2}^{+} > H _{2}$
• C. $H _{2} > H _{2}{ }^{+} > H _{2}^{-}$
• D. $H _{2}^{-} > H _{2} > H _{2}{ }^{+}$

Answer 1

Answer: (B)

Though bond order for $H _{2}^{+}$and $H _{2}^{-}$is same $( B . O = O .5), H _{2}^{-}$is slightly less stable than $H _{2}^{+}$because $H _{2}^{-}$has one electron in the antibonding orbital resulting in repulsion ( less stable). Thus bond length order is $H _{2}^{-} > H _{2}^{+} > H _{2}$