How do you write ionic compounds? And then how do you name the ionic compounds?

Na(+) and Cl(-) = NaCl
is sodium chloride ( ide added to end of word chlorine; ide instead of ire )

Na(+) and PO4(3-) = Na3PO4

need three Na(+) to ionically bond to phosphate. Since phosphate is a polyatomic ion it has one name, so the compound is,

sodium phosphate

and so on