Question

Calculate the bond order of $O_2^{-}$.

Answer 1

Calculation of bond order of $O_2^{-}$

Step 1: Calculating the total number of electrons in $O_2^{-}$
The number of electrons in O = 8
The number of electrons in ${\mathrm{O}}_2$ = 16
The number of elctelectronsrons in $O_2^{-}$ = 17

Step 2: Determination of electronic configuration of $O_2^{-}$
${\left[\mathrm{\sigma }\right(1\mathrm{s}\left)\right]}^2{\left[{\mathrm{\sigma }}^{\ast }\right(1\mathrm{s}\left)\right]}^2{\left[\mathrm{\sigma }\right(2\mathrm{s}\left)\right]}^2{\left[{\mathrm{\sigma }}^{\ast }\right(2\mathrm{s}\left)\right]}^2{\left[\mathrm{\sigma }\right(1\mathrm{pz}\left)\right]}^2{\left[\mathrm{\pi }\right(2\mathrm{px}\left)\right]}^2{\left[\mathrm{\pi }\right(2\mathrm{py}\left)\right]}^2{\left[{\mathrm{\pi }}^{\ast }\right(2\mathrm{px}\left)\right]}^2{\left[{\mathrm{\pi }}^{\ast }\right(2\mathrm{py}\left)\right]}^1$

Step 3: Determining the number of electrons in bonding molecular orbitals
The number of bonding electrons = 10

Step 4: Determining the number of electrons in anti-bonding molecular orbitals
The number of anti-bonding electrons = 7

Step 5: Calculation of bond order
Bond order = $\frac{\mathrm{Number}\mathrm{of}\mathrm{electrons}\mathrm{in}\mathrm{bonding}-\mathrm{Number}\mathrm{of}\mathrm{electrons}\mathrm{in}\mathrm{antibonding}}{2}$
Bond order = $\frac{10-7}{2}$
Bond order = $\frac{3}{2}$
Bond order = 1.5

Hence, the bond order for $O_2^{-}$ is 1.5.