Basic Difference (Short Answer)
Electron gain enthalpy is a measurable thermodynamic quantity for an isolated gaseous atom, while electronegativity is a relative tendency of an atom in a bonded state to attract electrons.
Electron Gain Enthalpy
- Defined as the enthalpy change when an electron is added to an isolated gaseous atom to form a gaseous anion.
- It is usually represented as: X(g) + e^- -> X^-(g), delta H
- It is an absolute, experimentally measurable quantity with units (usually kJ mol\(^{-1}\)).
- It refers to atoms in the gaseous, uncombined state.
Electronegativity
- Defined as the tendency of an atom in a molecule to attract the shared pair of electrons towards itself.
- It is a relative, dimensionless number placed on scales such as the Pauling scale.
- It cannot be measured directly; it is calculated or assigned from various properties (bond energies, ionization enthalpies, etc.).
- It refers only to atoms in the bonded state within molecules or ions.
Key Point in LaTeX
\[ \text{Electron gain enthalpy}:\ \text{thermodynamic, measurable, isolated atom} \] \[ \text{Electronegativity}:\ \text{relative, dimensionless, bonded atom in a molecule} \]