Molecular formula of sodium sulphate from Criss cross method

Na2SO4

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

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."

fe 55.85 g/mol and h2o 18.02 g/mol.