Identify the transition element

Options

A. `1s^2,2s^2,2p^6,3s^2,3p^5,4s^1`
B. `1s^2,2s^2,2p^6,3s^2,3p^6,3d^2,4s^2`
C. `1s^2,2s^2,2p^6,3s^2,3p^6,3d^10,4s^2,4p^2`
D. `1s^2,2s^2,2p^6,3s^2,3p^6,3d^10,4s^24p^1`

Answer

To identify the transition element, we need to understand what defines a transition element and how to recognize it based on its electronic configuration.

### Step-by-Step Solution:

1. **Understand the Definition of Transition Elements**:
- Transition elements are defined as the d-block elements in the periodic table. They are characterized by the presence of d electrons in their electronic configuration.

2. **Know the General Electronic Configuration**:
- The general electronic configuration for transition elements is given as:
\[ \text{Noble gas} \, \text{[Xe, Kr, Ar, etc.]} \, (n-1)d^{1-10} \, ns^{0-2} \]
- Here, the last electron enters the d orbital.

3. **Analyze Each Option**:
- **Option 1**: No d orbital present.
- If the electronic configuration does not show any d electrons, it cannot be a transition element.
- **Option 2**: \(1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 3d^2, 4s^2\)
- This configuration shows that the last electrons are entering the d orbital (3d), which indicates that it is a transition element.
- **Option 3**: Last electron enters the p orbital.
- If the last electron configuration ends in p, it indicates a p-block element, not a transition element.
- **Option 4**: Last electron also enters the p orbital.
- Similar to option 3, this indicates a p-block element.

4. **Conclusion**:
- After analyzing all options, the only configuration that fits the criteria for a transition element is **Option 2**.

### Final Answer:
The transition element is found in **Option 2**: \(1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 3d^2, 4s^2\).