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

Concept: Transition elements are defined as elements that have:

• Partially filled $d$ orbitals in the atomic state, or
• Form at least one ion with partially filled $d$ orbitals.

Step 1: Check Assertion (A). Zinc (Zn), Cadmium (Cd), and Mercury (Hg) have completely filled $d^{10}$ configurations. They do not form ions with partially filled $d$ orbitals. Hence, they are not considered transition elements. Assertion is true.
Step 2: Check Reason (R). These elements have: \[ d^{10} \text{ configuration in ground state and common oxidation states} \] So, reason is also true.
Step 3: Check if Reason explains Assertion. Since the definition of transition elements requires partially filled $d$ orbitals, having completely filled $d$ orbitals explains why Zn, Cd, Hg are not transition elements. Thus, Reason correctly explains Assertion.