Consider the equation for the formation of a kidney stone. 2Na3 PO4 (aq) + 3CaCl2 (aq) =
Ca3(PO4)2 (s) + 6NaCl (aq)

Is each reactant bonded ionically or covalently?

How do you know?

Ionically, because they are ionic compounds

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.