Which of the following pairs of elements would have a negative electron gain enthalpy ?
(i) O or F (ii) F or Cl

Explanation

To determine which pairs of elements would have a negative electron gain enthalpy, we need to analyze the electron affinity of each element in the pairs provided.

### Step-by-Step Solution:

1. **Understanding Electron Gain Enthalpy**:
- Electron gain enthalpy is the energy change that occurs when an electron is added to a neutral atom in the gaseous state. A negative electron gain enthalpy indicates that energy is released when an electron is added, which is generally favorable.

2. **Analyzing the First Pair (O or F)**:
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