The electron-electron coalescence I(0) and counterbalance E(0) densities are probability densities of finding any two electrons, respectively, at the same position and at the reflection points in the three-dimensional space. For a single Slater determinant wave function, these electron-pair properties are shown to be exactly expressible in terms of the spin-traced one-electron density function rho(r) and its orbital components rho(i)(r): I(0)=(1/4){[rho]-Delta(I)} and E(0)=2{[rho]-Delta(E)}, where [rho] is the average electron density, and Delta(I) and Delta(E) are linear combinations of overlaps between two orbital densities, that depend on the electronic configuration and the LS multiplet state of the atom under consideration. For the atoms He through Ne in their experimental ground state, the explicit forms of Delta(I) and Delta(E) are derived, and the electron-electron coalescence and counterbalance densities obtained from the numerical Hartree-Fock calculations are discussed. (C) 1997 American Institute of Physics. [S0021-9606(97)00847-7].