The l^N configuration is described as a collection of ¹/₂N(N-1) electron pairs, with the angular momenta of the electrons of each pair being coupled to the (2l+1) SL terms of l². In this way, a set of parameters is defined which can be visualised as the energies of these particular SL terms. The parameters represent the effects of two-particle excitations on the l^N configuration to second order. Moreover, they turn out, after a minor modification, to form an orthogonal set. The number of pairs multiplied by the average pair energy proves to be equal to the average energy of the full l^N configuration. Inner products of general two-particle operators are calculated and conditions for their orthogonality are derived. For the d^N configurations, two orthogonal three-body operators are added in order to obtain a complete set of electrostatic parameters. A simple general procedure is sketched that allows for the determination of the contributions of physical excitations to the various orthogonal parameters. This is illustrated by the s to d case. Values of all the matrix elements used are given.