4. Electron Sharing and      Covalent Bonds  

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.

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