The electron gain enthalpy of oxygen is `"______"` that of sulphur.

Explanation

To determine the relationship between the electron gain enthalpy of oxygen and sulfur, we need to analyze the electronic configurations and the factors affecting electron gain enthalpy.

### Step-by-Step Solution:

1. **Identify the Electronic Configurations**:
- Oxygen (O) has the electronic configuration: \(1s^2 2s^2 2p^4\).
- Sulfur (S) has the electronic configuration: \(1s^2 2s^2 2p^6 3s^2 3p^4\).

2. **Understand the Concept of Electron Gain Enthalpy**:
- Electron gain enthalpy is the amount of energy released when an electron is added to a neutral atom in the gaseous state. A more negative value indicates a greater tendency to gain an electron.

3. **Analyze the Subshells**:
- In oxygen, the added electron goes into the 2p subshell, while in sulfur, it goes into the 3p subshell.
- The 2p subshell is smaller in size compared to the 3p subshell.

4. **Consider the Size and Inter-electronic Repulsion**:
- The smaller size of the 2p subshell leads to greater inter-electronic repulsion when an additional electron is added.
- In sulfur, the 3p subshell is larger, which means the added electron experiences less repulsion from the existing electrons.

5. **Conclusion**:
- Due to the smaller size of the 2p subshell and the greater inter-electronic repulsion in oxygen, the electron gain enthalpy of oxygen is less negative (or less favorable) compared to that of sulfur.
- Therefore, the electron gain enthalpy of oxygen is **less than** that of sulfur.

### Final Answer:
The electron gain enthalpy of oxygen is **less than** that of sulfur.