Question

AX is a covalent diatomic molecule where A and X are second row elements of periodic table. Based on Molecular orbital theory, the bond order of AX is 2.5. The total number of electrons in AX is _________. (Round off to the Nearest Integer).

Hint:

A quick shortcut for bond orders of diatomic species between 8-20 electrons: 14e⁻ (B.O. 3), 13/15e⁻ (B.O. 2.5), 12/16e⁻ (B.O. 2).

Answer 1

Correct Answer: 15

Step 1: Bond order 2.5 is typically observed for species with 11, 13, or 15 electrons.
Step 2: Common diatomic molecules of second-row elements: $NO$ has $7 + 8 = 15$ electrons. $N_2^+$ has $14 - 1 = 13$ electrons.
Step 3: For $NO$ (15 electrons), Bond Order $= \frac{10 - 5}{2} = 2.5$. For $N_2^+$ (13 electrons), Bond Order $= \frac{9 - 4}{2} = 2.5$. Since AX is a neutral molecule "AX", $NO$ (15 electrons) is the most likely candidate.