Atomic and Molecular Negative Ions

An upper bound is given for the maximum number, $N_c$, of negative particles (fermions or bosons or a mixture of both) of charge $-e$ that can be bound to an atomic nucleus of charge $+\mathrm{ze}$. If $z$ is integral then $N_c<~2z$. In particular, this is the first proof that ${\mathrm{H}}^{--}$ is not stable. For a molecule, $N_c<~2Z+K-1$, where $K$ is the number of atoms in the molecule and $Z$ is the total nuclear charge.