Chemistry - CHEMICAL BONDING Question with Solution | TestHub

${\mathrm{H}}_2,\mathrm{}\mathrm{L}{\mathrm{i}}_2,\mathrm{}{\mathrm{B}}_2$are not equally stable. Li atom is much larger in size than H-atom. The bond order in$\mathrm{L}{\mathrm{i}}_2$is much larger than bond length in${\mathrm{H}}_2.$Moreover,$\mathrm{L}{\mathrm{i}}_2$molecule has two electrons in the antibonding molecular orbital while${\mathrm{H}}_2$has no electrons in the antiobinding molecular orbital. Thus,$\mathrm{L}{\mathrm{i}}_2$is less sable than$${\text{H}}_{\text{2}}\text{(Bond}\text{energy}\text{of}{\text{Li}}_{\text{2}}\text{=}\text{110}\text{kJ}{\text{mol}}^{-\text{2}}\text{+}\text{Bond}\text{energy}\text{of}{\text{H}}_{\text{2}}\text{=}\text{438}\text{kJ}{\text{mol}}^{-\text{1}}\text{)}$$Boron atom is smaller than lithium atom but larger than hydrogen atom. The${\mathrm{B}}_2$is more stable than$\mathrm{L}{\mathrm{i}}_2$but less stable than${\text{H}}_{\text{2}}\text{(Bond}\text{energy}\text{of}{\text{B}}_{\text{2}}\text{=}\text{290}\text{kJ}{\text{mol}}^{\text{-1}}\text{)}$