On Mulliken scale, the average of ionisation potential and electron affinity is known as ________.

Explanation

To solve the question, we need to identify what the average of ionization potential and electron affinity is known as according to the Mulliken scale. Here’s the step-by-step solution:

### Step 1: Understand the Terms
- **Ionization Potential (IP)**: This is the energy required to remove an electron from an atom in its gaseous state.
- **Electron Affinity (EA)**: This is the energy change that occurs when an electron is added to a neutral atom in its gaseous state.

### Step 2: Write the Formula
According to the Mulliken scale, the average of ionization potential and electron affinity is calculated using the formula:
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