Odd-Electron Molecule
A species containing an unpaired electron, so that its total electron count is odd and no octet structure is possible.
Unit
Dimensionless
In depth
Also called free radicals, these species are paramagnetic and usually highly reactive because pairing the lone electron releases energy. Some, such as nitric oxide, are stabilised by delocalisation and are stable enough to serve as biological signalling molecules.
Examples in the real world
NO and NO₂ in the atmosphere, ClO· radicals that destroy ozone, and chlorine radicals in photochemical chlorination.