Spin-extended Hartree-Fock calculations of atomicgJfactors

$g_J$-factor corrections for the ground states of the first-row atoms and sodium are calculated by use of spin-extended Hartree-Fock (SEHF) wave functions. The present results are compared with Hartree-Fock values and experimental $g_J$ factors. The theoretical SEHF $g_J$ factors show a deviation from the experimental ones which increase very regularly from lithium to fluorine. these discrepancies are believed to arise from the neglect of correlation effects, and they indicate that the previous success of the Hartree-Fock theory in the cases of oxygen and fluorine is fortuitous. Hartree-Fock values are also presented for the $g_J$-factor corrections of the ground states of the second-row atoms, and for potassium, rubidium, bromine, and iodine.