The energy released when an electron is added to a neutral gaseous atom is called`"………."`of atom.

Explanation

To solve the question, "The energy released when an electron is added to a neutral gaseous atom is called '……….' of atom," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Concept**: The question asks about the energy change that occurs when an electron is added to a neutral gaseous atom. This process involves the addition of an electron to an atom, which can either release energy or require energy.

2. **Defining the Term**: The energy released during this process is known as "electron affinity." Electron affinity refers to the amount of energy that is released when an electron is added to a neutral atom in the gas phase.

3. **Alternative Terminology**: Electron affinity is also referred to as "electron gain enthalpy." Both terms can be used interchangeably, but they describe the same phenomenon.

4. **Characteristics of Electron Affinity**:
- The value of electron affinity is generally negative, indicating that energy is released when the electron is added.
- In some cases, the electron affinity can be positive, meaning that energy must be supplied to add the electron.
- Chlorine has one of the highest electron affinities among all elements, which means it releases a significant amount of energy when it gains an electron.

5. **Final Answer**: Therefore, the energy released when an electron is added to a neutral gaseous atom is called "electron affinity" or "electron gain enthalpy."