identify polyatomic ions in gaianation.netical formulas. Create the correct formula for ionic compounds through polyatomic ions. Use the rules because that naming ionic compounds v polyatomic ions.

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Polyatomic Ions

Some ion consist of teams of atoms bonded together and also have an overall electric charge. Because these ion contain an ext than one atom, castle are called polyatomic ions. Polyatomic ions have actually characteristic formulas, names, and also charges that need to be memorized. For example, NO3− is the nitrate ion; it has one nitrogen atom and also three oxygen atoms and also an overall 1− charge. Table (PageIndex1) list the most common polyatomic ions.

Table (PageIndex1) part Polyatomic ions NameFormula
ammonium ion NH4+
acetate ion C2H3O2− (also written CH3CO2−)
carbonate ion CO32−
chromate ion CrO42−
dichromate ion Cr2O72−
hydrogen lead carbonate ion (bicarbonate ion) HCO3−
cyanide ion CN−
hydroxide ion OH−
nitrate ion NO3−
nitrite ion NO2−
permanganate ion MnO4−
phosphate ion PO43−
hydrogen phosphate ion HPO42−
dihydrogen phosphate ion H2PO4−
sulfate ion SO42−
hydrogen sulfate ion (bisulfate ion) HSO4−
sulfite ion SO32−

The dominance for building formulas for ionic compound containing polyatomic ion is the exact same as for formulas containing monatomic (single-atom) ions: the confident and an adverse charges have to balance. If an ext than one of a specific polyatomic ion is needed to balance the charge, the entire formula for the polyatomic ion need to be enclosed in parentheses, and the numerical subscript is inserted outside the parentheses. This is to display that the subscript uses to the entire polyatomic ion. An example is Ba(NO3)2.

Writing Formulas for Ionic compound Containing Polyatomic Ions

Writing a formula for ionic link containing polyatomic ions also involves the same steps as because that a binary ionic compound. Write the symbol and charge the the cation complied with by the symbol and also charge of the anion.

Example (PageIndex1): Calcium Nitrate

Write the formula for calcium nitrate.


Criss cross MethodWrite the formula because that calcium nitrate
1. Create the symbol and also charge that the cation (metal) very first and the anion (nonmetal) second. (ceCa^2+ : : : : : ceNO_3^-)
2. Transpose only the variety of the optimistic charge to become the subscript the the anion and also the number only of the an adverse charge to come to be the subscript the the cation.

Example (PageIndex3): specify name Ionic Compounds

Write the proper name because that each ionic compound.

(NH4)2S AlPO4, Fe3(PO4)2



a. The ammonium ion has actually a 1+ charge and also the sulfide ion has a 2− charge.

Two ammonium ions must balance the charge on a single sulfide ion.

The compound’s surname is ammonium sulfide.

ammonium sulfide

b. The ions have actually the exact same magnitude of charge, among each (ion) is required to balance the charges.

The name of the link is aluminum phosphate.

aluminum phosphate

c. Neither fee is an exact multiple that the other, for this reason we need to go to the least typical multiple that 6.

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To gain 6+, three iron(II) ions are needed, and to get 6−, 2 phosphate ions are necessary .