To tear apart one mole of H₂ molecules into two moles of H atoms requires 103.24 kcal of energy; thus we say that the bond energy of the H-H bond is 103.24 kcal/mole. We can represent H₂ molecules and H atoms on an energy-level diagram as shown on the right hand side of this page, where the vertical direction symbolizes increasing energy (and less stability). When we tear H₂ molecules apart, we store energy in the atoms in the same way that we store potential energy in a boulder when we roll it uphill. This energy is released when the atoms form a bond, or when the boulder rolls downhill.