Artificial atoms, i.e., systems of excess electrons confined in semiconductor quantum dots, are studied by the unrestricted Hartree-Fock method. We consider a spherical quantum dot embedded in an insulating matrix and assume a confinement potential in a form of spherical potential well of radius R and depth V0. The calculations have been performed for few- and many-electron artificial atoms with the number of electrons from 1 to 20. We have shown that bound many-electron states of atomlike properties are created in quantum dots if the values of R and V0 are sufficiently large. The critical values of R and V0 for the binding of N electrons in the quantum dots have been determined. We have found that the subsequent shells of the artificial atoms are filled by electrons according to the Hund rule. The characteristic behavior resulting from the full and half-filling of the shells is clearly visible in the dependence on the number of electrons of the calculated chemical potential, addition energy, and electric capacitance of the quantum dots. The present results have been compared with those of the classical Thomson model of atoms and applied to the quantum dots made of Si and GaAs.