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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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