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Q & A: ionic bonds

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Most recent answer: 10/22/2007
Q:
I need a brief explanation of how ionic and covalent bonds either share or transfer electrons.
- Clayton (age 15)
Dickinson HS, Dickinson, TX
A:
Purely covalent bonds, like the ones in an O2 molecule, have electrons spending equal times near each nucleus. There's no net charge trasfer from one atom to the other. The energy is lowered because the quantum states of the electrons can spread out over both atoms, which lowers the energy for reasons which cannot be described classically.
In bonds where the two atoms are different, there's always a little tendency of the electrons to hang out a bit more around one of the atoms, so that the atoms are a little bit ionized, i.e. charged. In some cases, that tendency is very strong, so it's almost as if an electron had simply left one atom and joined the other, leaving a positive and negative ion to attract electrostatically, in a way that can be described classically. Of course the reason why the electron would stick so much better to one atom than to the other flows entirely from the details of the quantum states available to those electrons, and thus this aspect of ionic bonding also has no classical explanation.

Mike W.

(published on 10/22/2007)

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