Alkyl free radicals are either planar or pyramidal in structure.Spectroscopic evidences shows that methyl free radical(.CH3) is planar in shape ,thus it is conveniently described by sp2 hybridisation with the unpaired electron located primarily in p-orbital. But in case of substituted radicals like trifluoro methyl free radical increasing fluorine substitution causes the radical to go from planar sp2 hybridisation ( as in .CH3) to tetrahedral, sp3 hybridisation in (.CF3 )radical.