Based on a simple model, theoretical description of localized spins of hybridized electron states of donor impurities in the conduction band of asemiconductor has been developed. Equations are formulated and solved numerically that describe the concentration dependence of localized spins. It is shown that they can exist and reach maximal values in a certain interval of impurity concentration in the vicinity of its value, at which the Fermi energy of the electronic system coincides with the energy level of the donor impurity. The conclusions obtained are compared with the results of Anderson's theory.