Assertion :- The first ionization energy of Be is greater than that of B
2p- orbital is lower in energy when 2s- orbital.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion.
C. If Assertion is True, but the Reason is False.
D. If both Assertion & Reason are false

Answer

To solve the question, we need to analyze the assertion and the reason provided:

**Assertion:** The first ionization energy of Be is greater than that of B.

**Reason:** The 2p orbital is lower in energy than the 2s orbital.

### Step-by-Step Solution:

1. **Understand Ionization Energy:**
- Ionization energy is the energy required to remove an electron from an atom in its gaseous state. Generally, the higher the ionization energy, the more energy is required to remove an electron.

2. **Write Electronic Configurations:**
- For Beryllium (Be): The electronic configuration is \(1s^2 2s^2\).
- For Boron (B): The electronic configuration is \(1s^2 2s^2 2p^1\).

3. **Identify the First Ionization Process:**
- For Beryllium: The first ionization involves removing one electron from \(2s^2\), resulting in \(1s^2 2s^1\).
- For Boron: The first ionization involves removing one electron from \(2p^1\), resulting in \(1s^2 2s^2\).

4. **Compare the Ionization Energies:**
- Beryllium has a completely filled \(2s\) subshell, which is more stable. Removing an electron from a stable configuration requires more energy.
- Boron, on the other hand, has an electron in the \(2p\) subshell, which is less stable compared to a filled \(2s\) subshell.

5. **Conclusion on Assertion:**
- Since it requires more energy to remove an electron from Beryllium than from Boron, the assertion is true: the first ionization energy of Be is indeed greater than that of B.

6. **Evaluate the Reason:**
- The reason states that the 2p orbital is lower in energy than the 2s orbital. This is incorrect. In general, for the same principal quantum number, the energy of the s orbital is lower than that of the p orbital (2s < 2p).

7. **Final Conclusion:**
- The assertion is true, but the reason is false. Therefore, the correct answer is that the assertion is true and the reason is false.

### Final Answer:
Assertion is true, but the reason is false.

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