Predict the valence electron molecular orbital configurations for the following, and state whether they will be stable or unstable ions.

(a) \({\rm{N}}{{\rm{a}}_{\rm{2}}}^{{\rm{2 + }}}\)

(b) \({\rm{M}}{{\rm{g}}_{\rm{2}}}^{{\rm{2 + }}}\)

(c) \({\rm{A}}{{\rm{l}}_{\rm{2}}}^{{\rm{2 + }}}\)

(d) \({\rm{S}}{{\rm{i}}_{\rm{2}}}^{{\rm{2 + }}}\)

(e) \({\rm{P}}_{\rm{2}}^{{\rm{2 + }}}\)

(f) \({{\rm{S}}_{\rm{2}}}^{{\rm{2 + }}}\)

(g) \({{\rm{F}}_{\rm{2}}}^{{\rm{2 + }}}\)

(h) \({\rm{A}}{{\rm{r}}_{\rm{2}}}^{{\rm{2 + }}}\)

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.

(a)\({\rm{N}}{{\rm{a}}_{\rm{2}}}^{{\rm{2 + }}}\):

Molecular orbital configuration:

\({\left( {{\sigma _{1s}}} \right)^2}{\left( {{\sigma _{2s}}} \right)^2}{\left( {\sigma _{2s}^*} \right)^2}{\left( {{\sigma _{2px}}} \right)^2}{\left( {{\pi _{2py}},{\pi _{2pz}}} \right)^4}{\left( {\pi _{2py}^*,\pi _{2pz}^*} \right)^4}{\left( {\sigma _{2px}^*} \right)^2}{\left( {{\sigma _{3s}}} \right)^0}\)

Valence electron molecular orbital configuration:\({\left( {{\sigma _{3s}}} \right)^0}\)

The ion is unstable

(b)\({\rm{M}}{{\rm{g}}_2}^{2 + }\): Molecular orbital configuration:

\({\left( {{\sigma _{1s}}} \right)^2}{\left( {{\sigma _{2s}}} \right)^2}{\left( {\sigma _{2s}^*} \right)^2}{\left( {{\sigma _{2px}}} \right)^2}{\left( {{\pi _{2py}},{\pi _{2pz}}} \right)^4}{\left( {\pi _{2py}^*,\pi _{2pz}^*} \right)^4}{\left( {\sigma _{2px}^*} \right)^2}{\left( {{\sigma _{3s}}} \right)^2}\).

Valence electron molecular orbital configuration:\({\left( {{\sigma _{3s}}} \right)^2}\).

The ion is stable

(c)\({\rm{A}}{{\rm{l}}_2}^{2 + }\): Molecular orbital configuration:

\({\left( {{\sigma _{1s}}} \right)^2}{\left( {{\sigma _{2s}}} \right)^2}{\left( {\sigma _{2s}^*} \right)^2}{\left( {{\sigma _{2px}}} \right)^2}{\left( {{\pi _{2py}},{\pi _{2pz}}} \right)^4}{\left( {\pi _{2py}^*,\pi _{2pz}^*} \right)^4}{\left( {\sigma _{2px}^*} \right)^2}{\left( {{\sigma _{3s}}} \right)^2}\)

Valence electron molecular orbital configuration:

\({\left( {{\sigma _{3s}}} \right)^2}{\left( {\sigma _{3s}^*} \right)^2}\)

The ion is unstable.

(d)\({\rm{S}}{{\rm{i}}_2}^{2 + }\): Molecular orbital configuration:

\({\left( {{\sigma _{1s}}} \right)^2}{\left( {{\sigma _{2s}}} \right)^2}{\left( {\sigma _{2s}^*} \right)^2}{\left( {{\sigma _{2px}}} \right)^2}{\left( {{\pi _{2py}},{\pi _{2pz}}} \right)^4}{\left( {\pi _{2py}^*,\pi _{2pz}^*} \right)^4}{\left( {\sigma _{2px}^*} \right)^2}{\left( {{\sigma _{3s}}} \right)^2}{\left( {{\pi _{3py}},{\pi _{3pz}}} \right)^2}\).

Valence electron molecular orbital configuration:\({\left( {{\sigma _{3s}}} \right)^2}{\left( {\sigma _{3s}^*} \right)^2}{\left( {{\pi _{3py}},{\pi _{3pz}}} \right)^2}\).

The ion is stable.

(e)\({{\rm{P}}_2}^{2 + }\): Molecular orbital configuration:

\({\left( {{\sigma _{1s}}} \right)^2}{\left( {{\sigma _{2s}}} \right)^2}{\left( {\sigma _{2s}^*} \right)^2}{\left( {{\sigma _{2px}}} \right)^2}{\left( {{\pi _{2py}},{\pi _{2pz}}} \right)^4}{\left( {\pi _{2py}^*,\pi _{2pz}^*} \right)^4}{\left( {\sigma _{2px}^*} \right)^2}{\left( {{\sigma _{3s}}} \right)^2}{\left( {{\pi _{3py}},{\pi _{3pz}}} \right)^4}\)

Valence electron molecular orbital configuration:\({\left( {{\sigma _{3s}}} \right)^2}{\left( {\sigma _{3s}^*} \right)^2}{\left( {{\pi _{3py}},{\pi _{3pz}}} \right)^4}\)

The ion is stable.

(f)\({{\rm{S}}_2}^{2 + }\): Molecular orbital configuration:

\({\left( {{\sigma _{1s}}} \right)^2}{\left( {{\sigma _{2s}}} \right)^2}{\left( {\sigma _{2s}^*} \right)^2}{\left( {{\sigma _{2px}}} \right)^2}{\left( {{\pi _{2py}},{\pi _{2pz}}} \right)^4}{\left( {\pi _{2py}^*,\pi _{2pz}^*} \right)^4}{\left( {\sigma _{2px}^*} \right)^2}{\left( {{\sigma _{3s}}} \right)^2}{\left( {{\sigma _{3px}}} \right)^2}{\left( {{\pi _{3py}},{\pi _{3pz}}} \right)^4}\).

Valence electron molecular orbital configuration:\({\left( {{\sigma _{3s}}} \right)^2}{\left( {\sigma _{3s}^*} \right)^2}{\left( {{\sigma _{3px}}} \right)^2}{\left( {{\pi _{3py}},{\pi _{3pz}}} \right)^4}\).

The ion is stable.

(g)\({{\rm{F}}_2}^{2 + }\): Molecular orbital configuration:

\({\left( {{\sigma _{1s}}} \right)^2}{\left( {{\sigma _{2s}}} \right)^2}{\left( {\sigma _{2s}^*} \right)^2}{\left( {{\sigma _{2px}}} \right)^2}{\left( {{\pi _{2py}},{\pi _{2pz}}} \right)^4}{\left( {\pi _{2py}^*,\pi _{2pz}^*} \right)^2}\)

Valence electron molecular orbital configuration:

\({\left( {{\sigma _{2s}}} \right)^2}{\left( {\sigma _{2s}^*} \right)^2}{\left( {{\sigma _{2px}}} \right)^2}{\left( {{\pi _{2py}},{\pi _{2pz}}} \right)^4}{\left( {\pi _{2py}^*,\pi _{2pz}^*} \right)^2}\)

The ion is stable.

(h)\({\rm{A}}{{\rm{r}}_2}^{2 + }\): Valence electron molecular orbital configuration:

\({\left( {{\sigma _{3s}}} \right)^2}{\left( {\sigma _{3s}^*} \right)^2}{\left( {{\sigma _{3px}}} \right)^2}{\left( {{\pi _{3py}},{\pi _{3pz}}} \right)^4}{\left( {\pi _{2py}^*,\pi _{2pz}^*} \right)^4}\)

The ion is stable.