The element having greatest difference between its first and second ionization energies, is:

Options

A. Sc
B. Ca
C. Ba
D. K

Explanation

To determine the element with the greatest difference between its first and second ionization energies, we will analyze the ionization energies of the given elements: potassium (K), calcium (Ca), and scandium (Sc).

### Step 1: Understand Ionization Energy
Ionization energy is the energy required to remove an electron from an atom. The first ionization energy (IE1) is the energy needed to remove the first electron, while the second ionization energy (IE2) is the energy required to remove the second electron.

### Step 2: Analyze the Elements
1. **Potassium (K)**:
- Electronic configuration: 1s² 2s² 2p⁶ 3s¹
- IE1: Removing the outermost electron (4s¹) is relatively easy.
- IE2: Removing the second electron (from the filled 3p and 3s subshells) is much harder because it requires breaking into a stable electron configuration.

2. **Calcium (Ca)**:
- Electronic configuration: 1s² 2s² 2p⁶ 3s²
- IE1: Removing one electron from the outermost shell (3s²) is easier.
- IE2: Removing the second electron (from the filled 3s subshell) is more difficult, but not as much as potassium.

3. **Scandium (Sc)**:
- Electronic configuration: 1s² 2s² 2p⁶ 3s² 3p¹
- IE1: Removing one electron from the outermost shell (3p¹) is relatively easy.
- IE2: Removing the second electron (from the filled 3s subshell) is also not as difficult as potassium.

### Step 3: Compare the Differences
- For **Potassium (K)**:
- IE1 is low, and IE2 is very high due to the stable noble gas configuration after the first ionization.
- Difference = IE2 - IE1 is very large.

- For **Calcium (Ca)**:
- The difference between IE1 and IE2 is significant but not as large as potassium.

- For **Scandium (Sc)**:
- The difference is smaller compared to potassium and calcium.

### Conclusion
The element with the greatest difference between its first and second ionization energies is **Potassium (K)**.

### Final Answer
**Potassium (K)** has the greatest difference between its first and second ionization energies.

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