The coefficient formula_17 is smaller than the binding energy possessed by the nucleons with respect to their neighbors (formula_27), which is of order of 40 MeV. This is because the larger the number of nucleons in the nucleus, the larger their kinetic energy is, due to the Pauli exclusion principle. If one treats the nucleus as a Fermi ball of formula_28 nucleons, with equal numbers of protons and neutrons, then the total kinetic energy is formula_29, with formula_30 the Fermi energy which is estimated as 38 MeV. Thus the expected value of formula_17 in this model is formula_32, not far from the measured value.