To investigate the effect of divalent cations, we melted a set of sodium silicate baseline glasses with different concentrations of Ca2+, Mg2+, and Zn2+. We doped each of these basic glass matrices with several different amounts of Er3+ cations. These samples have been characterized in terms of absorption spectra, luminescence spectra, and experimental lifetime of the erbium metastable state. We also fabricated planar waveguides using Ag+/Na+ ion-exchange process. Characteristic parameters of the waveguides such as the number of modes, the refractive index change, the depth of the diffused region, and the propagation loses were measured. The mutual replacements of the divalent cations influenced the electron donor power (basicity) of oxygen atoms coordinating metal ions in glass. Measured optical spectra, lifetime values, and waveguiding parameters reflected the changes in glass basicity. To quantify the individual effects of Ca2+, Mg2+, and Zn2+, we calculated composition-property models based on polynomial functions with multiple variables. Correlation coefficients R2 varied from 0.991 to 1.000 indicating good linear correlations between the parameters and composition. The evaluation of glass component effects on the studied parameters enabled us quantify the chemical influence of the divalent cations. We discussed this influence using the optical basicity theory that predicts the variations of the electron donor power of oxygen atoms with glass composition. The knowledge of component effects is very useful for the effective formulation of new glass compositions. New Er glasses containing Zn2+ and/ or Mg2+ as divalent cations are promising materials for optical waveguide amplifiers.