Which of the following will have the most nagative electron gain enthalpy and which the least negative ?
`P, S, Cl, F`
Explain your answer.

Explanation

To determine which of the elements (P, S, Cl, F) has the most negative and the least negative electron gain enthalpy, we need to analyze the trends in electron gain enthalpy across the periodic table.

### Step-by-Step Solution:

1. **Understanding Electron Gain Enthalpy**:
- Electron gain enthalpy is defined as the amount of energy released when an electron is added to a neutral atom in the gaseous state. This process is generally exothermic, meaning energy is released, and thus the electron gain enthalpy is usually negative.

2. **Periodic Trends**:
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