Least difference between IE2 and IE1 will be found in:

Options

A. Li
B. B
C. Be
D. C

Answer

To determine which element has the least difference between its first ionization energy (IE1) and second ionization energy (IE2), we need to analyze the electronic configurations and the stability of the electrons being removed.

### Step-by-Step Solution:

1. **Understanding Ionization Energy**:
- Ionization energy is the energy required to remove an electron from an atom. The first ionization energy (IE1) is for removing the first electron, while the second ionization energy (IE2) is for removing the second electron.

2. **Identify the Elements**:
- We will consider the elements mentioned: Lithium (Li), Beryllium (Be), Boron (B), and Carbon (C).
- Their electronic configurations are:
- Lithium (Li): 1s² 2s¹
- Beryllium (Be): 1s² 2s²
- Boron (B): 1s² 2s² 2p¹
- Carbon (C): 1s² 2s² 2p²

3. **Analyze the Removal of Electrons**:
- For **Li**: Removing the first electron (IE1) from 2s¹ leaves a stable 1s² configuration. The second electron (IE2) would be removed from the 1s², which requires significantly more energy due to the increased nuclear charge acting on fewer electrons.
- For **Be**: Removing the first electron (IE1) from 2s² leaves 1s² 2s¹. The second electron (IE2) is removed from the same 2s orbital, but the electron-electron repulsion is less significant here as both electrons are in the same subshell.
- For **B**: The first electron (IE1) is removed from 2p¹, and the second (IE2) is removed from 2s², which is a more stable configuration.
- For **C**: The first electron (IE1) is removed from 2p², and the second (IE2) is removed from 2p¹, which is also a stable half-filled configuration.

4. **Comparing IE1 and IE2**:
- The difference between IE1 and IE2 is generally smaller when the removal of the second electron comes from a similar energy level or subshell.
- In the case of **Beryllium (Be)**, the removal of the second electron from the same 2s subshell (after the first electron is removed) results in a smaller difference between IE1 and IE2 compared to the other elements.

5. **Conclusion**:
- The least difference between IE2 and IE1 will be found in **Beryllium (Be)**.

### Final Answer:
The least difference between IE2 and IE1 will be found in **Beryllium (Be)**.