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).

Answer 1

$NO$ bond order :
$B.O.=\frac{1}{2}(N_b-N_a)$
$NO$ :
$\sigma 1s^2{\sigma }^{\ast }1s^2\sigma 2s^2{\sigma }^{\ast }2s^2\sigma 2p_z^2\pi 2p_x^2\pi 2p_y^2{\pi }^{\ast }2p_x^1$
$B.O.=\frac{1}{2}(10-5)=2.5$
The compound $AX$ is $NO$ its bond order is 2.5 and it has total 15 electrons.

Note: Total number of electrons equal to 13 will also have the 2.5 bond order. But in this case neutral diatomic molecule will not be possible.