Which of the following will have the most negative 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 electron gain enthalpy and which has the least negative, we can follow these steps:

### Step 1: Understand Electron Gain Enthalpy
Electron gain enthalpy is the energy change when an atom gains an electron. A more negative value indicates a greater tendency to gain an electron.

### Step 2: Identify the Periodic Trend
As we move from left to right across a period in the periodic table, the atomic size decreases. This decrease in size generally leads to an increase in the electron gain enthalpy (more negative value) because the added electron experiences a stronger attraction to the nucleus.

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