Question

Assertion (A) The highest oxidation state of osmium is $+8$.
Reason (R) Osmium is a $5d$-series element.

• A. Both $A$ and $R$ are correct; $R$ is the correct explanation of $A$.
• B. Both $A$ and $R$ are correct; $R$ is not the correct explanation of $A$.
• C. $A$ is correct; $R$ is incorrect.
• D. $R$ is correct; $A$ is incorrect.

Answer 1

Answer: (B)

Both Assertion and Reason are correct but Reason is not the correct explanation of Assertion. The highest oxidation state of osmium is $+8$ due to its ability to expand their octet by using its all 8 electrons ($2$ from $6s$ and $6$ from $5d$ ).