`M_((g))+ eto M_((g))^(-)+ E`
In the above equation, E represents

Options

A. electron affinity
B. electronegativity
C. first ionisation potential
D. second lonisation potential

Explanation

To solve the question, we need to analyze the given equation and understand the terms involved. The equation is:

\[ M_{(g)} + e^- \rightarrow M_{(g)}^{-} + E \]

### Step-by-Step Solution:

1. **Identify the Components**:
- \( M_{(g)} \) represents a neutral gaseous metal atom.
- \( e^- \) represents an electron.
- \( M_{(g)}^{-} \) represents the anion formed when the metal atom gains an electron.

2. **Understand the Reaction**:
- The reaction shows a neutral metal atom \( M \) gaining an electron to form a negatively charged ion \( M^{-} \).
- The process of gaining an electron typically involves the release of energy.

3. **Define the Term E**:
- In this context, \( E \) represents the energy released when the neutral atom gains an electron.
- This energy is specifically defined as **electron affinity**.

4. **Review the Options**:
- **Option A: Electron Affinity** - This is the energy released when an atom gains an electron.
- **Option B: Electronegativity** - This is a measure of an atom's ability to attract shared electrons in a chemical bond.
- **Option C: First Ionization Potential** - This is the energy required to remove the most loosely bound electron from a neutral atom.
- **Option D: Second Ionization Potential** - This is the energy required to remove an electron from a positively charged ion.

5. **Conclusion**:
- Since \( E \) corresponds to the energy released during the formation of a negative ion from a neutral atom, the correct answer is **Option A: Electron Affinity**.

### Final Answer:
E represents **Electron Affinity**.