Which one of the following elements has the highest ionisation energy?

Options

A. `[Ne]3s^2 3p^1`
B. `[Ne]3s^2 3p^3`
C. `[Ne]3s^2 3p^2`
D. `[Ar]3d^(10)4s^2 4p^2`

Answer

To determine which element has the highest ionization energy, we will analyze the electronic configurations of the given elements and their stability.

### Step-by-Step Solution:

1. **Understanding Ionization Energy**:
- Ionization energy is the energy required to remove an electron from an isolated gaseous atom.
- Elements with stable electron configurations (like fully filled or half-filled orbitals) tend to have higher ionization energies because removing an electron from these configurations requires more energy.

2. **Analyzing the Options**:
- We need to look at the electronic configurations provided and identify which configuration is stable (half-filled or fully filled).

3. **Option 1: Neon (Ne)**
- Electronic configuration: 1s² 2s² 2p⁶ (fully filled)
- Since it is fully filled, it has a high ionization energy, but we need to compare it with other options.

4. **Option 2: Arsenic (As)**
- Electronic configuration: [Ar] 4s² 3d¹⁰ 4p³ (3p³ is half-filled)
- Half-filled configurations are stable, so this element will have a high ionization energy.

5. **Option 3: Silicon (Si)**
- Electronic configuration: [Ne] 3s² 3p²
- This configuration is neither half-filled nor fully filled, indicating lower stability and thus lower ionization energy.

6. **Option 4: Argon (Ar)**
- Electronic configuration: [Ne] 3s² 3p⁶ (fully filled)
- Similar to Neon, it has a high ionization energy due to its fully filled configuration.

7. **Comparison of Ionization Energies**:
- Neon and Argon both have fully filled configurations, which means they have high ionization energies.
- Arsenic has a half-filled configuration, which gives it a higher ionization energy than elements with neither half-filled nor fully filled configurations (like Silicon).
- However, between Neon and Argon, they both have high ionization energies, but we need to consider their atomic sizes as well.

8. **Conclusion**:
- Among the options, the element with the highest ionization energy is **Arsenic (As)** due to its half-filled configuration, which is more stable than the fully filled configurations of Neon and Argon when considering the context of the question.

### Final Answer:
**Arsenic (As) has the highest ionization energy among the given options.**