The formation of anion from a neutral atom `X` is favoured by:

Options

A. high electron affinity
B. large size of `X`
C. low ionisation potential
D. high charge on anion `X`

Answer

To determine the factors that favor the formation of an anion from a neutral atom \( X \), we need to analyze the given options step by step.

### Step-by-Step Solution:

1. **Understanding Anion Formation**:
- An anion is formed when a neutral atom gains one or more electrons. The ability of an atom to gain electrons is influenced by several factors.

2. **Evaluating High Electron Affinity**:
- **Definition**: Electron affinity is the amount of energy released when an electron is added to a neutral atom.
- **Analysis**: A high electron affinity indicates that the atom has a strong tendency to accept an electron. Therefore, if atom \( X \) has high electron affinity, it will favorably form an anion.
- **Conclusion**: This option is correct.

3. **Evaluating Larger Size**:
- **Definition**: The size of an atom refers to the distance from the nucleus to the outermost electrons.
- **Analysis**: As the atomic size increases, the distance between the nucleus and the outermost electrons also increases. This results in a weaker attraction between the nucleus and the incoming electron, making it less likely for the atom to gain an electron.
- **Conclusion**: This option is incorrect.

4. **Evaluating Low Ionization Potential**:
- **Definition**: Ionization potential (or ionization energy) is the energy required to remove an electron from a neutral atom.
- **Analysis**: A low ionization potential means that the atom can easily lose an electron to form a cation (positive ion). This indicates a tendency to lose electrons rather than gain them, which does not favor anion formation.
- **Conclusion**: This option is incorrect.

5. **Evaluating High Charge on Anion**:
- **Definition**: The charge on an anion refers to the number of extra electrons it has gained.
- **Analysis**: A high charge on an anion leads to increased electron-electron repulsion, making the anion less stable and less likely to form. Thus, a high charge on the anion does not favor the acceptance of additional electrons.
- **Conclusion**: This option is incorrect.

### Final Conclusion:
The formation of an anion from a neutral atom \( X \) is favored by **high electron affinity**. Therefore, the correct answer is the first option.

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