A quantum-mechanical vanational calculation is made for the molecule HF, based on the ionic model, the fluorine negative ion being polarized on the whole by the proton. Brown's numerical results for the Hartrce-Fock functions of the fluorine ion are used. The calculated results do not agree well with the experimental results, which indicates that, even for this most polar molecule, the above model serves only for a very poor representation of the motion of the electrons in the molecule.