Which of the following have no unit?

Options

A. electronegativity
B. electron gain enthalpy
C. ionisation enthalpy
D. all of the above

Answer

To determine which of the following concepts has no unit, we can analyze the properties mentioned in the video transcript.

### Step-by-Step Solution:

1. **Understanding Electronegativity**:
- Electronegativity is defined as the tendency of an atom to attract shared electrons in a chemical bond.
- Since it is a relative measure of this tendency, it does not have a physical dimension or unit associated with it.

2. **Analyzing Other Concepts**:
- **Ionization Energy**: This is the energy required to remove an electron from an isolated gaseous atom. It is measured in electron volts (eV) or kilojoules per mole (kJ/mol), which means it has units.
- **Electron Gain Enthalpy**: This is the energy change when an electron is added to an isolated gaseous atom. It is also measured in electron volts (eV) or kilojoules per mole (kJ/mol), indicating that it has units as well.
- **Enthalpy**: Generally refers to the total heat content of a system, and it also has units (e.g., joules or kilojoules).

3. **Conclusion**:
- Among the properties discussed, only electronegativity is unitless. Therefore, the answer to the question is that electronegativity has no unit.

### Final Answer:
Electronegativity has no unit.

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