In comparison to boron, berylium has :

Options

A. (A) lesser nuclear charge and greater first ionisation enthalpy
B. (B) greater nuclear charge and greater first ionisation enthalpy
C. (C) greater nuclear charge and lesser first ionisation enthalpy
D. (D) lesser nuclear charge and lesser first ionisation ethalpy.

Explanation

To solve the question "In comparison to boron, beryllium has:", we need to analyze the properties of both elements, specifically their nuclear charge and first ionization enthalpy.

### Step-by-Step Solution:

1. **Identify the Atomic Numbers and Electronic Configurations**:
- Beryllium (Be) has an atomic number of 4 and an electronic configuration of 1s² 2s².
- Boron (B) has an atomic number of 5 and an electronic configuration of 1s² 2s² 2p¹.

2. **Compare Nuclear Charge**:
- The nuclear charge is determined by the atomic number (Z).
- For beryllium, Z = 4, and for boron, Z = 5.
- Since beryllium has a lower atomic number, it has a lower nuclear charge compared to boron.

3. **Compare First Ionization Enthalpy**:
- The first ionization enthalpy is the energy required to remove the most loosely bound electron from an atom.
- Beryllium has a stable electronic configuration (full 2s orbital), while boron has a partially filled 2p orbital.
- Full-filled orbitals are more stable than partially filled orbitals. Therefore, it requires more energy to remove an electron from beryllium than from boron.
- Thus, beryllium has a higher first ionization enthalpy compared to boron.

4. **Summarize the Findings**:
- In comparison to boron, beryllium has:
- **Lesser nuclear charge** (due to lower atomic number).
- **Greater first ionization enthalpy** (due to stable electronic configuration).

### Final Answer:
In comparison to boron, beryllium has lesser nuclear charge and greater first ionization enthalpy.

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