ABSTRACT
The simple picture of a superatom based on electronic structure formed from the valence electrons of a cluster of metal atoms is a powerful one. This chapter explores the nature of a few well-studied examples, in order to summarise the ways in which some molecules do and do not conform to the general ideas about superatoms. The concept of a ‘superhalogen’ was demonstrated in a pair of 1981 papers by Gutsev and Boldyrev, in which they used then state of the art electronic structure theory to calculate the electron affinities of the molecules BeCl3, BCl4, MgCl3, AlCl4, SiCl5 and PCl6, and similarly constructed fluorine and oxygen containing molecules. As in the case of the superhalogens, the molecular character of superalkalis makes them rather different than the metal cluster based superatoms that have already discussed. In particular, the superalkalis are not in general spherical species, with some of them even adopting linear geometries.
