Question

Criss cross method for Ammonium Phosphate thank you

Answer 1

ions are NH4+1and  PO4-3. The generic equation is (NH4+1)x(PO4-3)y. Again there are many pairs of subscripts that will allow the result to be zero: 12:4, 9:3, 6:2 and 3:1. The lowest ratio is 3:1. The charges add to zero: 3(+1) +1(-3)=0. Which gives the generic  formula (NH4+1)3(PO4-3)1. The NH4+1 is polyatomic with the subscript of 3 and therefor the parenthesis must be retained. The SO4-2 is polyatomic and requires the use of parenthesis, if the subscript is bigger than “1". The final equation is (NH4)3PO4.

Answer 2

NH4 = +1

PO4 = -3

Hence, it's (NH4)3PO4