Which of the following is transition element ?

Options

A. P
B. Zn
C. Cu
D. Na

Answer

To determine which of the given elements is a transition element, we need to analyze the electronic configurations of each element and check for the presence of an incomplete d-orbital. Here’s a step-by-step solution:

### Step-by-Step Solution:

1. **Understand Transition Elements**:
Transition elements are defined as elements that have an incomplete d-orbital in their electronic configuration.

2. **List the Elements**:
The elements given are:
- Phosphorus (P)
- Zinc (Zn)
- Copper (Cu)
- Sodium (Na)

3. **Determine the Electronic Configuration**:
- **Phosphorus (P)**:
- Atomic number = 15
- Electronic configuration = 1s² 2s² 2p⁶ 3s² 3p³
- There is no d-orbital present.

- **Zinc (Zn)**:
- Atomic number = 30
- Electronic configuration = 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰
- The d-orbital is completely filled (3d¹⁰).

- **Copper (Cu)**:
- Atomic number = 29
- Electronic configuration = 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁹
- However, due to stability, it is often represented as 4s¹ 3d¹⁰, which means the d-orbital is not completely filled (3d has 9 electrons).

- **Sodium (Na)**:
- Atomic number = 11
- Electronic configuration = 1s² 2s² 2p⁶ 3s¹
- There is no d-orbital present.

4. **Identify the Transition Element**:
- From the analysis, phosphorus and sodium do not have d-orbitals, and zinc has a completely filled d-orbital.
- Copper has an incomplete d-orbital (3d⁹), making it the transition element.

5. **Conclusion**:
The transition element among the given options is **Copper (Cu)**.