What do you mean by successive electron gain enthalpies ? Why is the second electron gain enthalpy of an atom positive .

Explanation

### Step-by-Step Solution

1. **Definition of Successive Electron Gain Enthalpies**:
- Successive electron gain enthalpies refer to the amount of energy released when electrons are added one after another to an isolated gaseous atom. Each time an electron is added, the energy change associated with that process is measured. The first electron gain enthalpy (ΔEG1) is the energy change when the first electron is added, the second electron gain enthalpy (ΔEG2) is the energy change when the second electron is added, and so on.

2. **Understanding the Sign of Electron Gain Enthalpies**:
- The first electron gain enthalpy (ΔEG1) is usually negative because energy is released when an electron is added to a neutral atom, making it more stable. For example, when an electron is added to a neutral atom X, it becomes negatively charged (X⁻), and energy is released in this process.

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