Question

Assertion (A): Transition metals show their highest oxidation state with oxygen.
Reason (R): The ability of oxygen to form multiple bonds to metals.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

Oxygen forms M=O multiple bonds, which let metals reach their highest oxidation states.

Answer 1

The Correct Option is A

Step 1: Judge each statement separately.
As always, decide if the assertion stands alone, decide if the reason stands alone, and then test whether the reason is the real cause. The focus here is why oxygen in particular brings out very high oxidation states.

Step 2: Test the assertion.
The highest oxidation states of transition metals turn up in their oxides, for example manganese reaches $+7$ in $\mathrm{Mn_2O_7}$ and osmium reaches $+8$ in $\mathrm{OsO_4}$. So the assertion is true.

Step 3: Test the reason.
Oxygen is small and very electronegative, and importantly it can form double bonds to the metal. These extra $\mathrm{M{=}O}$ bonds feed extra electron density to the metal and let it climb to a very high oxidation state. So the reason is true.

Step 4: Do they connect.
This very ability of oxygen to form multiple bonds is what pulls the metal up to its top state, so the reason explains the assertion.
\[ \boxed{\text{Option (A): both true, R explains A}} \]