The electromagnetic properties of ground and excited states of nuclei with an odd number of particles and holes outside the closed shells are described in the j-j coupling shell model. The residual interaction between the valence particles and holes causes two different configuration mixing: (a) one where the valence particles and holes are scattered to higher shell model states, and (b) ones where the valence particles and holes excite particles out of the core. The electromagnetic properties of odd-even nuclei are sensitive to the correct treatment of both types of configuration mixing. In this paper the matrix elements of the nuclear Hamiltonian evaluated using the basis of configuration mixing states of types (a) and (b), and the resulting eigenvalue equations, have been exactly calculated. The matrix elements of the electromagnetic multipole operators calculated with the resulting eigenvectors of type (b) are then related to the deviation observed between the experimental and valence expectation values.