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

Options

A. If both assertion and reason are true annd the reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but the reason is false
D. if assertion is false but the reason is true

Answer

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

### Step 1: Understand the Assertion
The assertion states that the first ionization energy of Beryllium (Be) is greater than that of Boron (B).

- **Ionization Energy**: This is the energy required to remove the outermost electron from an atom.
- **Electronic Configuration**:
- Beryllium (Be): 1s² 2s²
- Boron (B): 1s² 2s² 2p¹

**Analysis**:
Beryllium has a stable electronic configuration with a fully filled 2s subshell. In contrast, Boron has one electron in the 2p subshell. When Boron loses this p-electron, it achieves a stable configuration (1s²). Therefore, it is easier for Boron to lose this p-electron compared to Beryllium losing one of its s-electrons. This indicates that the ionization energy of Beryllium is indeed greater than that of Boron.

### Conclusion for Assertion:
The assertion is **True**.

### Step 2: Understand the Reason
The reason states that the 2p-orbital is lower in energy than the 2s-orbital.

**Analysis**:
According to the n + l rule:
- For the 2p orbital: n = 2, l = 1 → n + l = 3
- For the 2s orbital: n = 2, l = 0 → n + l = 2

The higher the n + l value, the higher the energy of the orbital. Since the n + l value for the 2p orbital (3) is greater than that for the 2s orbital (2), this means that the 2p orbital is actually higher in energy than the 2s orbital.

### Conclusion for Reason:
The reason is **False**.

### Final Conclusion:
- The assertion is **True**.
- The reason is **False**.

Thus, the correct answer is that the assertion is true, and the reason is false.

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