unrepaired? A "free radical" is any atom or molecule which has an "unpaired electron" in the outer ring. An "unpaired electron" will also always mean that there is an odd number since "pairing" of electrons goes by 2s.
however if we are talking molecules we can have covalent bonding which surely means that they can be paired but still be an odd number of electrons in the outer shell because of the sharing of electrons rather than the transfer of ionic bonding.