Сеrtain approximations of mobility coefficients for the metal atoms’ ions in parent vapor are investigated,a comparison between experimental data was drawn, and Monte Carlo calculations are performed. Incontrast to ions of noble gases, ions and atoms of alkali metals have a number of features that must beconsidered when building a model of ion-atom collisions. Approximations for mobility coefficients forthe alkali ions in parent vapor are given, they are valid not only in the weak electric field limit, but also instrong fields, when ion heating enacts in external electric field. On the basis of the analysis of MonteCarlo calculations and comparing them with experimental data on the mobility of alkali metal ions innoble gases, we obtain approximation formulas for the mobility of alkali metal ions in parent vapors. Theparameters found earlier for the approximation of the drift velocity of ions of noble gases are also givenas a reference material. The parameters obtained in this work for the approximation of the mobility ofalkali metal ions in parent vapors can be used to estimate the characteristics of a gas-discharge plasma.