Por qué dos iones sodio reemplazan un ion de calcio o de magnesio

Why two sodium ions replace a calcium or magnesium ion

Explanation:

Two sodium ions will replace a calcium or magnesium ion because, a sodium ion is has just one positive charge, it has lost an electron. A calcium or magnesium ion has two electrons.

           Sodium ion  -   Na⁺

            Magnesium ion - Mg²⁺      Calcium ion Ca²⁺

For a replacement in the lattice of a mineral to occur between sodium and any of magnesium or calcium, two of it must be used so as to balance the charge properly;

                 Na⁺   +  Na⁺ will replace Mg²⁺ or Ca²⁺ in crystal space

This will allow for perfect charge replacement.

it is the most commonly accepted one