Assertion : $\mathrm{S}_2 \mathrm{O}_7^{2-}$ and $\mathrm{Cr}_2 \mathrm{O}_7^{2-}$ both exist. Reason : Both have same valence electrons.

• A

  If both assertion and reason are true and reason is the correct explanation of assertion.
• Correct answer
  B

  If both assertion and reason are true but reason is not the correct explanation of assertion.
• C

  If assertion is true but reason is false.
• D

  If both assertion and reason are false.

Solution

Both having same structure and same valance electrons.

Hence, the correct answer is option: 'B'.