Question

The correct bond order in the following species is.

• A. O₂ O₂⁺ O₂²⁺
• B. O₂²⁺ O₂⁺ O₂^-
• C. O₂²⁺ , O₂⁺ , O₂
• D. ^{O₂+ O₂- O₂2+}

Answer 1

The correct option is B

O₂²⁺ O₂⁺ O₂^-

The correct option is B.

Explanation of the correct option:

1. Bond order (B.O) shows the number of chemical bonds present between the atoms.
2. The formula B.O is, $\mathrm{Bond}\mathrm{Order}=1/2[{\mathrm{N}}_{\mathrm{b}}-{\mathrm{N}}_{\mathrm{a}}]$
3. Where ${\mathrm{N}}_{\mathrm{b}}$ is the number of bonding electrons and ${\mathrm{N}}_{\mathrm{a}}$ is the number of antibonding electrons

The electronic configuration of the ${{\mathbf{O}}_{\mathbf{2}}}^{\mathbf{+}\mathbf{2}}$ ion-containing 18 electrons can be expressed as:

1. $\mathrm{\sigma }1{\mathrm{s}}^2{\mathrm{\sigma }}^{*}1{\mathrm{s}}^2\mathrm{\sigma }2{\mathrm{s}}^2{\mathrm{\sigma }}^{*}2{\mathrm{s}}^2\mathrm{\sigma }2{{\mathrm{p}}_{\mathrm{z}}}^2\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{x}}}^2\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{y}}}^2\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{x}}^{*}}^0\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{y}}^{*}}^0$
2. $\mathrm{Bond}\mathrm{order}=26-0=3$

The electronic configuration of the ${\mathbf{O}}_{\mathbf{2}}$ containing 16 electrons can be expressed as:

1. $\mathrm{\sigma }1{\mathrm{s}}^2{\mathrm{\sigma }}^{*}1{\mathrm{s}}^2\mathrm{\sigma }2{\mathrm{s}}^2{\mathrm{\sigma }}^{*}2{\mathrm{s}}^2\mathrm{\sigma }2{{\mathrm{p}}_{\mathrm{z}}}^2\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{x}}}^2\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{y}}}^2\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{x}}^{*}}^1\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{y}}^{*}}^1$
2. $\mathrm{Bond}\mathrm{Order}=28-4=2$

The electronic configuration of the ${{\mathbf{O}}_{\mathbf{2}}}^{\mathbf{+}}$ containing 16 electrons can be expressed as:

1. $\mathrm{\sigma }1{\mathrm{s}}^2{\mathrm{\sigma }}^{*}1{\mathrm{s}}^2\mathrm{\sigma }2{\mathrm{s}}^2{\mathrm{\sigma }}^{*}2{\mathrm{s}}^2\mathrm{\sigma }2{{\mathrm{p}}_{\mathrm{z}}}^2\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{x}}}^2\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{y}}}^2\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{x}}^{*}}^2\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{y}}^{*}}^0$
2. $\mathrm{Bond}\mathrm{Order}=28-3=2.5$

The electronic configuration of the ${{\mathbf{O}}_{\mathbf{2}}}^{\mathbf{-}}$ion-containing 17 electrons can be expressed as:

1. $\mathrm{\sigma }1{\mathrm{s}}^2{\mathrm{\sigma }}^{*}1{\mathrm{s}}^2\mathrm{\sigma }2{\mathrm{s}}^2{\mathrm{\sigma }}^{*}2{\mathrm{s}}^2\mathrm{\sigma }2{{\mathrm{p}}_{\mathrm{z}}}^2\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{x}}}^2\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{y}}}^2\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{x}}^{*}}^2\mathrm{\pi }2{{\mathrm{p}}_{\mathrm{y}}^{*}}^1$
2. $\mathrm{Bond}\mathrm{Order}=28-5=1.5$

Hence, ${{\mathbf{O}}_{\mathbf{2}}}^{\mathbf{-}}$contains 3 electrons in the anti-bonding orbital and therefore it requires less energy to remove an electron from an anti-bonding orbital.

Hence, the correct bond order in the following species is ${{\mathbf{O}}_{\mathbf{2}}}^{\mathbf{-}}\mathbf{<}{{\mathbf{O}}_{\mathbf{2}}}^{\mathbf{+}}\mathbf{<}{{\mathbf{O}}_{\mathbf{2}}}^{\mathbf{2}\mathbf{+}}$.