Which of the following have no unit?

Options

A. Electronegativity
B. Electron gain enthalpy
C. Ionisation enthalpy
D. Metallic character.

Explanation

To determine which of the given terms has no unit, we will analyze each term one by one.

### Step-by-Step Solution:

1. **Electronegativity**:
- Definition: Electronegativity is the tendency of an atom to attract shared electrons in a chemical bond.
- Analysis: Since it describes a tendency and is a relative measure, electronegativity has no unit. It is often represented on a scale (like the Pauling scale) but does not have a physical unit associated with it.

2. **Electron Gain Enthalpy**:
- Definition: Electron gain enthalpy is the amount of energy released when an electron is added to a neutral atom in the gas phase.
- Analysis: This is a measure of energy, and it is expressed in units such as kilojoules per mole (kJ/mol). Therefore, it has a unit.

3. **Ionization Enthalpy**:
- Definition: Ionization enthalpy is the amount of energy required to remove an electron from a neutral atom in the gas phase.
- Analysis: Like electron gain enthalpy, ionization enthalpy is also a measure of energy and is expressed in units such as kilojoules per mole (kJ/mol). Thus, it has a unit.

4. **Metallic Character**:
- Definition: Metallic character refers to the tendency of an element to lose electrons and form positive ions (cations).
- Analysis: This is also a tendency and does not have a specific unit. It is a qualitative measure rather than a quantitative one.

### Conclusion:
From the analysis above, we can conclude that **Electronegativity** and **Metallic Character** have no unit.

### Final Answer:
- **Electronegativity** and **Metallic Character** have no unit.

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