# Effect of light on ionic compounds

If I had an ionic molecule which needed $\pu{4 eV}$ to break the ionic bond, a $\pu{7 eV}$ photon is shot at it. If it is absorbed by the molecule and breaks, where does the rest of the energy go?

• I'm not confident enough to post as an answer, but I'm guessing as heat. Or maybe some electrons end up in an excited state, resulting in light emission when they go back. We'll see when someone more knowledgable comes along :) – Brian Feb 11 '13 at 18:46
• The question as posed is confusing. An ionic bond is really just electrostatic attraction between a cation and its neighboring anion. You can speak of how much energy it would take to separate the ions to infinite distance given a starting distance. But 'breaking' the bond as is done photochemically with covalent bonds is not meaningful. – Rich Apodaca Feb 24 '13 at 0:44