The new experimental Coulomb sums values of 6Li and 7Li nuclei have been obtained at momentum transfers range q = 0.750¸ 1.000 fm-1 and q = 0.750¸ 1.125 fm-1, respectively, extending significantly the earlier reported momentum transfers range of Coulomb sums for these nuclei. The dependence of the 6Li and 7Li Coulomb sums on the momentum transferred is shown to differ substantially from same dependences for all the other investigated nuclei. It is suggested that the observed feature of the 6Li and 7Li Coulomb sums is related to a strong clusterization of these nuclei. The parameter qp corresponding to the value of the momentum transferred, at which the Coulomb sum ceases to grow and remains constant for larger momentum transfers, is introduced. The values of the parameter qp for the lithium isotopes nuclei were obtained (qp(7Li) = 1.20 ± 0.10fm-1 and qp(7Li) = 1.35 ± 0.10 fm-1), which are much lower than qp of 4He, 12C, 40Ca, 48Ca and 56Fe nuclei (qp » 2 fm-1). The graph represented the qp values of the nuclei as a function of the isolation parameter x, which characterizing the degree of nuclear clusterization, is constructed. The obtained graph shows the explicit proportionality of the qp dependence from the parameter x and predicts the qp value for the Coulomb sum of the 9Be nucleus not yet measured.