Question

Assertion: The highest oxidation state of osmium is $+8$.

Reason: Osmium is a $5$d-block element.

• A. Assertion is not true but reason is true.
  
• B. Both assertion and reason are false.
  
• C. Both assertion and reason are true but reason is not the correct explanation of assertion.
  
• D. Both assertion and reason are true, and reason is the correct explanation of the assertion.
  

Answer 1

The correct option is C Both assertion and reason are true but reason is not the correct explanation of assertion.


Analysing the assertion:

The electronic configuration of osmium is: $\left[Xe\right]4f^{14}5d^{6}6s^2$

It can show a maximum oxidation state of $+8$ because by doing so it acquires the stable configuration of completely filled $4f$ orbitals.

It is a transition element which shows the highest oxidation state of $+8$.

Analysing the reason:

Osmium is a heavier element and belongs to the $5d$ transition series.

Thus, due to the large size and less effective nuclear charge, osmium can show higher oxidation state.

So, the reason is also correct but not the correct explanation of the assertion.

Thus, both assertion and reason are true but reason is not the correct explanation of assertion.

Hence, option (B) is correct.