Question

Assertion (A): Zinc, cadmium and mercury are not considered as transition elements. Reason (R): These elements have completely filled $d$ orbitals in their ground state as well as in their common oxidation states. Choose the correct option:

• 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:

Transition element rule: Must have partially filled $d$ orbitals in atom or ion. Zn, Cd, Hg = $d^{10}$ → Not transition elements.

Answer 1

The Correct Option is A

The assertion in the given question states that zinc, cadmium, and mercury are not considered transition elements. The reason provided is that these elements have completely filled \(d\) orbitals in their ground state as well as in their common oxidation states.

1. Understanding Transition Elements: Transition elements are typically defined as those elements which have partially filled \(d\) orbitals. They are located in the central part of the periodic table, between the s-block and p-block elements. The key feature is the presence of an incomplete \(d\) sub-shell.
2. Electronic Configuration of Zinc, Cadmium, and Mercury:
   • Zinc (Zn): Its electronic configuration is \([Ar] \, 3d^{10} \, 4s^{2}\).
   • Cadmium (Cd): Its electronic configuration is \([Kr] \, 4d^{10} \, 5s^{2}\).
   • Mercury (Hg): Its electronic configuration is \([Xe] \, 4f^{14} \, 5d^{10} \, 6s^{2}\).
3. Explanation of Assertion and Reason:
   • Assertion (A) is true: Zinc, cadmium, and mercury are indeed not considered transition elements because they do not have partially filled \(d\) orbitals.
   • Reason (R) is true: The reason given is that these elements have completely filled \(d\) orbitals in both ground state and common oxidation states. This is correct.
   • Link between Assertion and Reason: The reason provided accurately explains why these elements are not classified as transition metals. The complete filling of \(d\) orbitals is directly related to their exclusion from the transition category, which requires at least one partially filled \(d\) orbital.

Therefore, the correct answer is: Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).