Atomic Structure

Abstract

Of course the hydrogen atom, discussed at length in Chapter Eleven, is a one-electron system, but it is not the only one. The ions He⁺ and Li²⁺ for example also possess one electron. It is appropriate to consider all such systems together, because their properties are similar. In many-electron atoms the picture, regrettably, is more complex, as electron-electron repulsion terms must be included in any expression for electron energy. It is only for one-electron systems that the energy-degeneracy of orbitals within a particular shell is retained (Figure 12.1). Not only are orbitals of (say) the 3-shell of higher energy than those of the 2-shell, but the ‘size’ of orbitals of the same type increases with energy. We have used the expression

$$$$

(11.8)