For an element `'A'` , the first ionisation energy will be numerically equal to `:`

Options

A. EA of A+
B. EA of A2+
C. IE of A2+
D. None of these

Explanation

To solve the question regarding the first ionization energy of an element 'A', we will follow these steps:

### Step-by-Step Solution:

1. **Understand Ionization Energy**:
- Ionization energy (IE) is defined as the energy required to remove one electron from the outermost shell of an atom or ion. For element 'A', the first ionization energy can be represented as:
\[ A \rightarrow A^+ + e^- \]
- Here, energy is supplied to remove an electron from the neutral atom 'A', resulting in a cation \(A^+\) and a free electron.

2. **Understand Electron Affinity**:
- Electron affinity (EA) is the energy released when an electron is added to an atom or ion. For the cation \(A^+\), the electron affinity can be represented as:
\[ A^+ + e^- \rightarrow A \]
- This process releases energy, which is the electron affinity of \(A^+\).

3. **Relate Ionization Energy and Electron Affinity**:
- The relationship between ionization energy and electron affinity can be expressed as:
\[ IE = -EA \]
- This means that the magnitude of the first ionization energy (IE1) is equal to the negative of the electron affinity (EA1) of the cation \(A^+\).

4. **Conclusion**:
- Therefore, the numerical value of the first ionization energy of element 'A' is equal to the electron affinity of \(A^+\).
- Thus, the correct answer to the question is that the first ionization energy of element 'A' will be numerically equal to the electron affinity of \(A^+\).

### Final Answer:
The first ionization energy of element 'A' is numerically equal to the electron affinity of \(A^+\).

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