Question

Which of the following oxoanions contains all equivalent M−O bonds?

• A. ${{\mathrm{MnO}}_4}^{-}$
• B. ${{\mathrm{CrO}}_4}^{2-}$
• C. ${\mathrm{Cr}}_2{{\mathrm{O}}_7}^{2-}$
• D. Both (A) and (B)

Answer 1

The correct option is D

Both (A) and (B)

Explanation for correct option:

D. Both (A) and (B)

Bond length:

• “Bond length is defined as the equilibrium distance between the nuclei of two bonded atoms in a molecule.”

A. ${{\mathrm{MnO}}_4}^{-}$:

• In the permanganate ion, all the Mn − O bonds are equivalent and they have the same bond length.
• The structure of ${{\mathrm{MnO}}_4}^{-}$ is given below:

B. ${{\mathrm{CrO}}_4}^{2-}$:

• In the chromate ion, all the Cr − O bonds are equivalent and they have the same bond length.
• The structure of ${{\mathrm{CrO}}_4}^{2-}$is given below:

Explanation for incorrect options:

C. ${\mathrm{Cr}}_2{{\mathrm{O}}_7}^{2-}$

• In dichromate ion, , two types of Cr − O bonds are present in which one has a bond length of $179\mathrm{pm}$ and the other has a bond length of $163\mathrm{pm}$.
• The structure of ${\mathrm{Cr}}_2{{\mathrm{O}}_7}^{2-}$is given below:H

Hence, the correct option is D i.e. Both (A) and (B).