Question

The bond order of $\text{Li}_2$ is _______ and it is _______.

• A. 1, diamagnetic
• B. 2, paramagnetic
• C. 1, paramagnetic
• D. 2, diamagnetic

Hint:

For light homonuclear diatomic molecules, if the total number of electrons is even (except for $B_2$ with 10 electrons and $O_2$ with 16 electrons), the molecule is almost always diamagnetic.

Answer 1

The Correct Option is A

Step 1: Write the molecular orbital configuration of Li2.
Lithium has 3 electrons, so Li2 has 6 electrons total, filling as \( \sigma1s^2 \sigma^{*}1s^2 \sigma2s^2 \).
Step 2: Compute the bond order.
Bond order is half the difference between bonding and antibonding electrons: here there are 4 bonding electrons (\( \sigma1s^2 \) and \( \sigma2s^2 \)) and 2 antibonding electrons (\( \sigma^{*}1s^2 \)).
\[ \text{Bond order} = \frac{4-2}{2} = 1 \]
Step 3: Determine the magnetic nature.
Every molecular orbital in this configuration is completely filled, meaning there are no unpaired electrons, so the molecule is diamagnetic.
\[ \boxed{1, \text{ diamagnetic}} \]