Enthalpy of atomization

The enthalpy of atomization is is the enthalpy change that accompanies the total seperation of all atoms in a chemical substance (either an elemental substance or a compound). This is often represented by the symbol ΔH_at^O. The associated standard enthalpy is known as the Standard enthalpy of atomization, ΔH_at^O/(kJ mol^-1), at 298K.

The enthalpy of atomization of gaseous H₂O is, for example, the sum of the HO—H and H—O bond dissociation enthalpies. The enthalpy of atomization of an elemental solid is exactly the same as the enthalpy of sublimation for any elemental solid that becomes a monatomic gas upon evaporation.