Which of the following is the correct order of ionisation energy?
(1) `Be^(+) gt Be` (2) `Be gt Be^(+)`
(3) `C gt Be` (4) `B gt Be`

Options

A. 2,3
B. 3,4
C. 1,3
D. 1,4

Explanation

To determine the correct order of ionization energy among the given options, we will analyze each pair of elements based on their electronic configurations and positions in the periodic table.

### Step-by-Step Solution:

1. **Understanding Ionization Energy (IE):**
Ionization energy is the energy required to remove an electron from an atom in its gaseous state. Generally, ionization energy increases across a period and decreases down a group in the periodic table.

2. **Analyzing the First Pair: `Be^(+)` vs. `Be`:**
- **Beryllium (Be)** has the electronic configuration of 1s² 2s².
- **Beryllium ion (Be⁺)** has lost one electron, resulting in the configuration of 1s² 2s¹.
- Since Be has a filled 2s orbital, it is more stable than Be⁺, which has a partially filled 2s orbital. Therefore, it takes more energy to remove an electron from Be than from Be⁺.
- **Conclusion:** `Be > Be^(+)` (Option 2 is correct).

3. **Analyzing the Second Pair: `C` vs. `Be`:**
- **Carbon (C)** has the electronic configuration of 1s² 2s² 2p².
- **Beryllium (Be)** has the electronic configuration of 1s² 2s².
- Carbon has a higher nuclear charge (6 protons) compared to Beryllium (4 protons), leading to a greater effective nuclear charge. This results in a smaller atomic radius for Carbon, which means the electrons are held more tightly.
- **Conclusion:** `C > Be` (Option 3 is correct).

4. **Analyzing the Third Pair: `B` vs. `Be`:**
- **Boron (B)** has the electronic configuration of 1s² 2s² 2p¹.
- **Beryllium (Be)** has the electronic configuration of 1s² 2s².
- Beryllium has a filled 2s orbital, while Boron has a partially filled 2p orbital. Removing an electron from Boron leads to a more stable configuration (similar to Be).
- Therefore, it requires less energy to remove an electron from Boron than from Beryllium.
- **Conclusion:** `Be > B` (Option 4 is incorrect).

5. **Final Conclusion:**
The correct order of ionization energy from the analysis is:
- `Be > Be^(+)`
- `C > Be`
- `Be > B`

Therefore, the correct options are:
- Option 2: `Be > Be^(+)`
- Option 3: `C > Be`
- Option 4: `Be > B` is incorrect.

### Final Answer:
The correct order of ionization energy is:
- **Option 2 and Option 3 are correct.**