What of the following is a transition element ?

Options

A. Hg
B. Zn
C. Cu
D. All of these

Explanation

To determine which of the following is a transition element, we need to understand the definition and characteristics of transition elements.

### Step-by-Step Solution:

1. **Understanding Transition Elements**: Transition elements are defined as elements that have partially filled d orbitals. They are typically found in the d-block of the periodic table.

2. **Identifying D-Block Elements**: The d-block elements include groups 3 to 12 of the periodic table. However, not all d-block elements are classified as transition elements.

3. **Criteria for Transition Elements**:
- Transition elements must have an incomplete d subshell in at least one of their oxidation states.
- They exhibit properties such as the ability to form colored compounds, variable oxidation states, and the formation of complex ions.

4. **Analyzing Specific Elements**:
- **Zinc (Zn)**: Atomic number 30, electronic configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰. The d orbital is completely filled (3d¹⁰), so Zinc is not a transition element.
- **Cadmium (Cd)**: Atomic number 48, electronic configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 4d¹⁰. The d orbital is completely filled (4d¹⁰), so Cadmium is not a transition element.
- **Mercury (Hg)**: Atomic number 80, electronic configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 5d¹⁰. The d orbital is completely filled (5d¹⁰), so Mercury is not a transition element.

5. **Conclusion**: Since Zinc, Cadmium, and Mercury all have completely filled d orbitals, they do not qualify as transition elements. Therefore, if there is another option provided (not mentioned in the transcript), that would be the transition element.