This paper discusses the use of the non-Euclidean heptakisoctahedral group, 7 O, of order 168, to study the atomic f shell of interest in lanthanide and actinide chemistry. In this group only the representations of the spherical harmonics of dimensions 0, 1, or 6 (mod 7) can be reduced to sums of irreducible representations (irreps). These include the S, F, I, K, and N spherical harmonics with ' values of 0, 3, 6, 7, and 10, respectively. The other spherical harmonics must be combined into pairs with total dimension a multiple of 7 in order to have representations reducible into sums of irreps of 7 O. Such pairs of interest in the atomic f shell include the PH and DG pairs of total dimension 14, the GM and HL pairs of total dimension 28, and the LQ and MO pairs of total dimension 42. If the subgroup chain SO(7) ' G 2 ' 7 O is used to study the atomic f shell, terms corresponding to these paired spherical harmonics, such as PH and DG pairs found in the highest spin f n configurations, appear together under a given irrep of SO(7) or G 2 .