Although we have focused so far on neutral closed-shell molecules, eFF should in principle be able to optimize cationic and anionic species and radicals as well. To calculate accurate bond dissociation energies, it is especially important to have a well-balanced description of radicals and closed shell species.
Consider the series of molecules , radical, and . Both and radical are expected to be planar and have similar bond length. Our force field reproduces bond lengths well (for , 1.095 versus 1.087 exact; for , 1.091 versus 1.079 exact).
eFF makes methyl radical less stable than it should be (adiabatic ionization potential is 64 kcal/mol versus 226.8 kcal/mol exact), as it is not capable of properly describing the radical electron, which should reside in a orbital. As in the case of multiple bonds, our force field compensates for its lack of functions by making the radical electron very diffuse and placing it above the molecular plane.
eFF makes methyl carbanion unbound relative to methyl radical. This is not a surprising result, since in reality methyl carbanion is only marginally more stable than methyl radical (1.8 kcal/mol energy difference ); high-level theoretical calculations  (1.6 kcal/mol energy difference found) with large basis sets and correlation included are necessary to show that methyl carbanion is a stable species relative to methyl radical.