Question

Determine the bond order of each member of the following groups, and determine which member of each group is predicted by the molecular orbital model to have the strongest bond.

(a) \({{\rm{H}}_{\rm{2}}}{\rm{,}}{{\rm{H}}_{\rm{2}}}{\rm{ + ,H}}_{\rm{2}}^{\rm{ - }}\)

(b) \({{\rm{O}}_{\rm{2}}}{\rm{,O}}_{\rm{2}}^{{\rm{2 + }}}{\rm{,O}}_{\rm{2}}^{{\rm{2 - }}}\)

(c) \({\rm{L}}{{\rm{i}}_{\rm{2}}}{\rm{,B}}{{\rm{e}}_{\rm{2}}}{\rm{ + ,B}}{{\rm{e}}_{\rm{2}}}\)

(d) \({{\rm{F}}_{\rm{2}}}{\rm{,\;}}{{\rm{F}}_{\rm{2}}}{\rm{ + ,}}\;\;\;{\rm{F}}_{\rm{2}}^{\rm{ - }}\)

(e) \({{\rm{N}}_{\rm{2}}}{\rm{,\;N}}_{\rm{2}}^{\rm{ + }}{\rm{,}}\;\;\;{\rm{N}}_{\rm{2}}^{\rm{ - }}\)

Short answer

(a)\({{\rm{H}}_2}\)has the highest bond order and thus has strongest bond.

(b)\({{\rm{O}}_2}^{2 + }\)has the highest bond order and thus has strongest bond.

(c)\({\rm{L}}{{\rm{i}}_2}\)has the highest bond order and thus has strongest bond.

(d)\({{\rm{F}}_2} + \)has the highest bond order and thus has strongest bond.

(e) \({{\rm{N}}_2}\) has the highest bond order and thus has strongest bond.

Step-by-step solution

Definition of bonding molecular orbital

Bonding orbitals are used in molecular orbital theory (MO) to describe the attractive interactions between the atomic orbitals of two or more atoms in a molecule

Finding bond for H2

Let us consider the below formula

bond order\( = \frac{{{\rm{ (number of bonding }}}}{{{\rm{ electrons) }} - {\rm{ (number of antibonding electrons) }}}}\)

The strength of the bond increases as the bond order increases.

(a)

\({{\rm{H}}_{\rm{2}}}\) has highest bond order and thus has strongest bond

Finding bond for \({{\bf{O}}_{\bf{2}}}^{{\bf{2}} + }\) 

b)

\({\rm{O}}_2^{2 + }\) has highest bond order and thus has strongest bond.

Finding bond for \({\bf{L}}{{\bf{i}}_{\bf{2}}}\)

c)

\({\rm{L}}{{\rm{i}}_2}\)has highest bond order and thus has strongest bond

Finding bond for \({{\bf{F}}_{\bf{2}}}^ + \) 

d)

\({{\rm{F}}_2}^ + \)has highest bond order and thus has strongest bond.

Finding bond for \({{\bf{N}}_{\bf{2}}}\)

e)

\({{\rm{N}}_2}\) has highest bond order and thus has strongest bond.