Question

Use the molecular orbital diagram shown to determine which of the following is most stable.

A. F2²⁺
B.  Ne2²⁺
C. F2^2-
D. O2²⁺
E. F2

Answer 1

Concepts and reason

Bond order of the molecule indicates the number of bond present between the pair of atoms.

Bond order is the measurement of the bond strength of a molecule.

An increase in the bond order shows the increase in the bond strength and so a stable compound.

Bond order can be calculated by using molecular orbital theory and molecular energy diagram.

Fundamentals

Molecular Orbital Theory

In molecular orbital theory, electrons stay in molecular orbital unlike valence bond theory where electrons stay in individual orbitals.

Molecular Orbitals

Linear combinations of atomic orbitals are called as molecular orbitals. These molecular orbitals are generally divided into two types:

(i)bonding orbitals

(ii)antibonding orbitals

Bond order in terms of molecular orbitals:

${\rm{bond}}\,{\rm{order}}\,{\rm{ = }}\,\frac{{{\rm{(Number}}\,{\rm{of}}\,{\rm{bonding}}\,{\rm{electrons - Number}}\,{\rm{of}}\,{\rm{anti}}\,{\rm{bonding}}\,{\rm{electrons)}}}}{{\rm{2}}}$

General Molecular Orbital Diagram

$\begin{array}{l}\\{\rm{Bond}}\,{\rm{order}}\,{\rm{of}}\,{{\rm{F}}_{\rm{2}}}^{{\rm{2 + }}}{\rm{ = }}\frac{{\rm{1}}}{{\rm{2}}}\left( {{\rm{8 - 4}}} \right)\\\\{\rm{ = 2}}\\\end{array}$

$\begin{array}{l}\\{\rm{Bond}}\,{\rm{order}}\,{\rm{of}}\,{\rm{N}}{{\rm{e}}_{\rm{2}}}^{{\rm{2 + }}}{\rm{ = }}\frac{{\rm{1}}}{{\rm{2}}}\left( {{\rm{8 - 6}}} \right)\\\\{\rm{ = 1}}\\\end{array}$

$\begin{array}{l}\\{\rm{Bond order of }}{{\rm{F}}_{\rm{2}}}^{{\rm{2 - }}}{\rm{ = }}\frac{{\rm{1}}}{{\rm{2}}}\left( {{\rm{8 - 8}}} \right)\\\\{\rm{ = 0}}\\\end{array}$

$\begin{array}{l}\\{\rm{Bond}}\,{\rm{order}}\,{\rm{of}}\,{{\rm{O}}_{\rm{2}}}^{{\rm{2 + }}}{\rm{ = }}\frac{{\rm{1}}}{{\rm{2}}}\left( {{\rm{8 - 2}}} \right)\\\\{\rm{ = 3}}\\\end{array}$

$\begin{array}{l}\\{\rm{Bond order of }}{{\rm{F}}_{\rm{2}}}{\rm{ = }}\frac{{\rm{1}}}{{\rm{2}}}\left( {{\rm{8 - 6}}} \right)\\\\{\rm{ = 1}}\\\end{array}$

${{\rm{O}}_{\rm{2}}}^{{\rm{2 + }}}\,{\rm{is}}\,{\rm{most}}\,{\rm{stable}}{\rm{.}}$

Ans:

${{\rm{O}}_{\rm{2}}}^{{\rm{2 + }}}\,{\rm{is}}\,{\rm{most}}\,{\rm{stable}}{\rm{.}}$