Enthalpy of atomization

The enthalpy of atomization (also atomisation in British spelling) is the enthalpy change that accompanies the total separation of all atoms in a chemical substance (either a chemical element or a chemical compound). This is often represented by the symbol Δ_atH or ΔH_at. All bonds in the compound are broken in atomization and none are formed, so enthalpies of atomization are always positive. The associated standard enthalpy is known as the Standard enthalpy of atomization, Δ_atH/(kJmol), at 298.15 K (or 25 degrees celsius) and 101.3 kPa.