Which of the following has/have not unit?

Options

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

Answer

To determine which of the given properties have no units, let's analyze each property step-by-step:

### Step 1: Electronegativity
- **Definition**: Electronegativity is the tendency of an atom to attract electrons towards itself when it is part of a compound.
- **Unit**: Electronegativity is measured on a relative scale (e.g., the Pauling scale) and does not have any physical units associated with it. It is a dimensionless quantity.

### Step 2: Electron Gain Enthalpy
- **Definition**: Electron gain enthalpy refers to the amount of energy released or absorbed when an electron is added to a neutral atom in the gas phase.
- **Unit**: This property is measured in joules per mole (kJ/mol), indicating that it has units.

### Step 3: Ionization Enthalpy
- **Definition**: Ionization enthalpy is the amount of energy required to remove an electron from a neutral atom in the gas phase.
- **Unit**: Similar to electron gain enthalpy, ionization enthalpy is also measured in joules per mole (kJ/mol), meaning it has units.

### Step 4: Metallic Character
- **Definition**: Metallic character refers to the tendency of an element to exhibit properties of metals, such as conductivity and malleability, and is often associated with the ability to lose electrons.
- **Unit**: Metallic character is a qualitative measure and does not have specific units. It is often assessed relative to other elements.

### Conclusion
From the analysis:
- **Properties without units**: Electronegativity and Metallic Character.
- **Properties with units**: Electron Gain Enthalpy and Ionization Enthalpy.

### Final Answer
Electronegativity and Metallic Character do not have units.

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