Which have the same number of s-electrons as the d-electrons in ` Fe^(2+)` ?

Options

A. Li
B. Ca
C. N
D. P

Answer

To solve the problem of identifying which element has the same number of s-electrons as the d-electrons in \( \text{Fe}^{2+} \), we can follow these steps:

### Step 1: Determine the electronic configuration of \( \text{Fe}^{2+} \)

1. **Identify the atomic number of iron (Fe)**: Iron has an atomic number of 26.
2. **Write the ground state electronic configuration of iron**: The configuration is \( 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^6 \).
3. **Determine the configuration of \( \text{Fe}^{2+} \)**: When iron loses two electrons to form \( \text{Fe}^{2+} \), the electrons are removed from the 4s orbital first. Thus, the configuration becomes \( 3d^6 \).

### Step 2: Count the d-electrons in \( \text{Fe}^{2+} \)

- The number of d-electrons in \( \text{Fe}^{2+} \) is 6 (from the \( 3d^6 \) configuration).

### Step 3: Analyze the given options for s-electrons

1. **Lithium (Li)**:
- Atomic number = 3
- Electronic configuration = \( 1s^2 2s^1 \)
- Total s-electrons = 2 + 1 = 3 (not equal to 6).

2. **Calcium (Ca)**:
- Atomic number = 20
- Electronic configuration = \( 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^0 \)
- Total s-electrons = 2 + 2 + 2 + 2 = 8 (not equal to 6).

3. **Nitrogen (N)**:
- Atomic number = 7
- Electronic configuration = \( 1s^2 2s^2 2p^3 \)
- Total s-electrons = 2 + 2 = 4 (not equal to 6).

4. **Phosphorus (P)**:
- Atomic number = 15
- Electronic configuration = \( 1s^2 2s^2 2p^6 3s^2 3p^3 \)
- Total s-electrons = 2 + 2 + 2 = 6 (equal to 6).

### Conclusion

The element that has the same number of s-electrons as the d-electrons in \( \text{Fe}^{2+} \) is **Phosphorus (P)**.

### Summary of the Solution:
- The d-electrons in \( \text{Fe}^{2+} \) = 6.
- The only element among the options that has 6 s-electrons is **Phosphorus**.