Examples:
SO42-= sulfate ion → H2SO4 = sulfuric acid
NO3–= nitrate ion → HNO3 = nitric acid
Before naming Oxoacids, we need to setup some rules to name the POLYATOMIC IONS. (ZONE IN GREY INDICATE THAT THESE ELEMENTS DO NOT FORM OXOACIDS

All ATE ions will have three oxygen atoms in their formula with the exceptions of the ones highlighted in the table above with the number 4 in pink, which will have four. Hence, Carbonate ion, Nitrate ion, Chlorate ion, Bromate ion, etc will have 3 oxygen atoms, but Phosphate, Sulphate, etc, will have 4 oxygen atoms in their molecule.
The number of negative charges will be 2 for the EVEN groups (Silicate, Sulphate, Carbonate, -belong to an even number-) the rest will have one, with the exceptions of B, P and As, that will have 3 negative charges.