Question

According to molecular orbital theory, which of the following is true with respect to $L{i}_2^{+}$ and $L{i}_2^{-}$?

• A. Both are unstable
• B. $L{i}_2^{+}$ is unstable and $L{i}_2^{-}$ is stable
• C. $L{i}_2^{+}$ is stable and $L{i}_2^{-}$ is unstable
• D. Both are stable

Answer 1

Answer: (C)

$L{i}_2^{+}$ is stable and $L{i}_2^{-}$ is unstable

Bond order of $L{i}^{+2}=\frac{1}{2}(n_b-n_a)=\frac{1}{2}(3-2)=0.5$

Bond order of $L{i}^{-2}=\frac{1}{2}(n_b-n_a)=\frac{1}{2}(4-3)=0.5$

Bond order of $L{i}^{+2}$=Bond order of $L{i}^{-2}$

Lesser the no. of antibonding $e^{-}$ $\left(n_a\right)$ greater the stability

$(n_a{)}_{L{i}^{2+}}<(n_a{)}_{L{i}^{2-}}$ $\Rightarrow$

$L{i}^{2+}$ is stable and $L{i}^{2-}$ is unstable.