D Block Elements

Concept: Transition elements are defined as elements that have:

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

Step 1: Check Assertion (A). Zinc (Zn), Cadmium (Cd), and Mercury (Hg) have completely filled configurations. They do not form ions with partially filled orbitals. Hence, they are not considered transition elements. Assertion is true.
Step 2: Check Reason (R). These elements have: So, reason is also true.
Step 3: Check if Reason explains Assertion. Since the definition of transition elements requires partially filled orbitals, having completely filled orbitals explains why Zn, Cd, Hg are not transition elements. Thus, Reason correctly explains Assertion.

Step 1: Analyze Assertion (A). Manganese exhibits a maximum oxidation state of +7 (e.g., in ). However, the statement says “in most of the transition elements,” which is incorrect because many transition elements do not reach +7 oxidation state. Assertion is false.
Step 2: Analyze Reason (R). Transition metals show variable oxidation states due to participation of both and electrons in bonding. Reason is true.