oxvampxo

i help to find the bond type of polyatomic ions but first i need to find the difference in electronegativity of them. I have no clue how to do this. ammonium sulfate (NH4)2SO4 magnesium phosphate Mg3(PO4) There are more but i want to know how to do those first. can anybody help me... i need to know how to do this this doesnt help me at all... whatever