The atomization energy of KrF2 (KrF2(g) → Kr(g) + 2F(g)) is 21.9 kcal/mol, giving an average Kr–F bond energy of only 11 kcal/mol, the weakest of any isolable fluoride. In comparison, difluorine is held together by a bond of 36 kcal/mol. Consequently, KrF2 is a good source of the extremely reactive and oxidizing atomic fluorine. It is thermally unstable, with a decomposition rate of 10% per hour at room temperature. Krypton difluoride is endothermic, with a heat of formation of 14.4 ± 0.8 kcal/mol measured at 93 °C.