Polyatomic Ions

Nomenclature : Polyatomic Ions

**Common Polyatomic Ions**
Charge	Name	Formula		Charge	Name	Formula		Charge	Name	Formula
+1	ammonium	NH₄¹⁺		-1	perchlorate	ClO₄^1-		-2	peroxide	O₂^2-
+2	uranyl	UO²⁺			chlorate	ClO₃^1-			thiosulfate	S₂O₃^2-
+2	vanadyl	VO²⁺			chlorite	ClO₂^1-			hydrogen phosphate	HPO₄^2-
-1	hydroxide	OH^1-			hypochlorite	ClO₁^1-			silicate	SiO₃^2-
	acetate or	CH₃COO^1-		-2	oxalate	C₂O₄^2-		-3	borate	BO₃^3-
	acetate or	C₂H₃O₂^1-			carbonate	CO₃^2-			arsenate	AsO₄^3-
	permanganate	MnO₄^1-			sulfate	SO₄^2-			arsenite	AsO₃^3-
	nitrate	NO₃^1-			sulfite	SO₃^2-			phosphate	PO₄^3-
	nitrite	NO₂^1-			chromate	CrO₄^2-			phosphite	PO₃^3-
	cyanide	CN^1-			dichromate	Cr₂O₇^2-

Polyatomic Anions Containing Oxygen

Many polyatomic anions are made up of an element (usually a nonmetal) and oxygen.
These carry an overall negative charge.
The anion is named by the root name of the non-oxygen element.
- e.g. NO₃^1- is nitr-ate
When two polyatomic ions contain the same non-oxygen element:
- the element with the higher oxidation number has the suffix -ate
- the element with the lower oxidation number has the suffix -ite

Ion	Oxidation #	Name		Ion	Oxidation #	Name
SO₄^2-	S is 6+	sulfate		NO₃^1-	N is 5+	nitrate
SO₃^2-	S is 4+	sulfite		NO₂^1-	N is 3+	nitrite

When more than two polyatomic ions contain the same non-oxygen element:
- the element with the highest oxidation number has the prefix per-
- the element with the lowest oxidation number has the prefix hypo-

Ion	Oxidation #	Name
ClO₄^1-	Cl is 7+	perchlorate
ClO₃^1-	Cl is 5+	chlorate
ClO₂^1-	Cl is 3+	chlorite
ClO₁^1-	Cl is 1+	hypochlorite

Sample Salts with Polyatomic Ions

BaSO₄	barium sulfate		KMnO₄	potassium permanganate		NH₄Cl	ammonium chloride
NaC₂O₄	sodium oxalate		AgNO₃	silver nitrate		PbCO₃	lead(II) carbonate
CuClO₄	copper(I) perchlorate		Zn₃(PO₄)₂	zinc phosphate		Fe(OH)₃	ferric hydroxide

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