Answer:
Na2SO4
Step-by-step explanation:
In the crisscross method, we can write the correct formula for an ionic compound by crossing over the numerical value of each of the ion charges to now serve as the subscript of the oppositely charged ion. Subsequently, the signs of the charges are dropped and the correct formula of the ionic substance is obtained.
For sodium sulphate;
Na ^+ SO4^2-
By crisscrossing and dropping the signs to obtain the subscripts we now have;
Na2SO4