Which of the following is not a transition element ?

Options

A. Zn
B. Ru
C. Ag
D. Pb

Answer

To determine which of the given options is not a transition element, we need to analyze the electronic configurations of each element listed: zinc, ruthenium, silver, and lead.

### Step 1: Identify the Elements and Their Atomic Numbers
- **Zinc (Zn)**: Atomic number 30
- **Ruthenium (Ru)**: Atomic number 44
- **Silver (Ag)**: Atomic number 47
- **Lead (Pb)**: Atomic number 82

### Step 2: Write the Electronic Configurations
1. **Zinc (Zn)**:
- Electronic configuration: \( [Ar] 4s^2 3d^{10} \)
- Zinc has a completely filled d-subshell (3d), which qualifies it as a transition element.

2. **Ruthenium (Ru)**:
- Electronic configuration: \( [Kr] 5s^1 4d^{7} \)
- Ruthenium has an incomplete d-subshell (4d), which qualifies it as a transition element.

3. **Silver (Ag)**:
- Electronic configuration: \( [Kr] 5s^1 4d^{10} \)
- Silver also has a partially filled d-subshell (4d), which qualifies it as a transition element.

4. **Lead (Pb)**:
- Electronic configuration: \( [Xe] 6s^2 4f^{14} 5d^{10} 6p^2 \)
- Lead has its outermost electrons in the p-subshell (6p) and does not have a partially filled d-subshell. Therefore, it is not considered a transition element.

### Conclusion
The element that is not a transition element among the options provided is **Lead (Pb)**.

### Final Answer
**Lead (Pb)** is not a transition element.

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