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).

In molecular orbital diagram, for the bond order 2.5, they should have a total of 15 electrons. Thus, the compound AX is NO (covalent compound).
The molecular orbital configuration of NO is: $\mathrm{\sigma }1{\mathrm{s}}^2{\mathrm{\sigma }}^{*}1{\mathrm{s}}^2\mathrm{\sigma }2{\mathrm{s}}^2{\mathrm{\sigma }}^{*}2{\mathrm{s}}^2\mathrm{\sigma }2{\mathrm{p}}_{\mathrm{z}}^2\left(\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{x}}}^2=\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{y}}}^2\right)\left({\mathrm{\pi }}^{*}2{{\mathrm{p}}_{\mathrm{x}}}^1={\mathrm{\pi }}^{*}2{{\mathrm{p}}_{\mathrm{y}}}^0\right)$

B.O=$\frac{1}{2}\left({\mathrm{N}}_{\mathrm{b}}-{\mathrm{N}}_{\mathrm{a}}\right)=\frac{1}{2}\left(10-5\right)=2.5$