# What is the formula of the compound formed when ammonium ions, NH_4 ^+, and phosphate ions, PO_4^(3-) combine?

${\left(N {H}_{4}\right)}_{3} P {O}_{4}$
This is because $N {H}_{4}^{+}$ has a charge of 1+, and $P {O}_{4}^{3 -}$ has a charge of 3-. The compound should have a neutral charge, so it takes three $N {H}_{4}^{+}$ to balance out $P {O}_{4}^{3 -}$.