(a) Ionization Enthalpy : The energy required to remove an electron from an isolated gaseous atom in its ground state is called ionization enthalpy. It is represented by ∆iH.
(b) Electron Gain Enthalpy: When an electron is added to a neutral gaseous atom to convert it into a negative ion, the enthalpy change accompanying the process is called electron gain enthalpy. The unit of electron gain enthalpy is kJ/mol.
