Polyatomic Ions

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Polyatomic Ions

Polyatomic Ions-A polyatomic ion is a molecule made up of 2 or more atoms that bears ionic groups, that is, a molecule with a charge.

Oxyanions- Negative polyatomic ions with oxygen

*Prefix*	*Suffix*	*Example*	*Names*
Per- (more than)	-ate (largest #)	ClO₄^-	perchlorate
	-ate (large #)	ClO₃^-	chlorate
	-ite (smaller #)	ClO₂^-	chlorite
Hypo- (less than)	-ite (smallest #)	ClO^-	hypochlorite

Other important polyatomic ions (from-http://www2.pvc.maricopa.edu/tutor/chem/chem130/nomenclature/polyatomicion.html)

Tips to memorize your polyatomic ions.

Determining the charge of a polyatomic ion

Polyatomic ions exist because the atoms contained in them with stable electron configurations. These are even number of electrons. If the total of the group numbers of the atoms is odd, it will need an odd number of electrons to make the total even. Therefore if the total is an odd #, the charge of the ion is 1- (phosphate is the only 3- you need to know). If the total of all the group numbers is even then the charge is also even. The charge would be 2-.

Common Polyatomic Ions

ion	name	ion	name	ion	name	ion	name	ion	name
+1 CHARGE		-1 CHARGE		-2 CHARGE		-3 CHARGE		-4 CHARGE
NH₄⁺	ammonium	H₂PO₃^-	dihydrogen phosphite	HPO₃^2-	hydrogen phosphite	PO₃^3-	phosphite	P₂O₇^4-	pyrophosphate
H₃O⁺	hydronium	H₂PO₄^-	dihydrogen phosphate	HPO₄^2-	hydrogen phosphate	PO₄^3-	phosphate
Hg₂²⁺	mercury(I)	HCO₃^-	hydrogen carbonate	CO₃^2-	carbonate	PO₂^3-	hypophosphite
		HSO₃^-	hydrogen sulfite	SO₃^2-	sulfite	AsO₃^3-	arsenite
		HSO₄^-	hydrogen sulfate	SO₄^2-	sulfate	AsO₄^3-	arsenate
		NO₂^-	nitrite	S₂O₃^2-	thiosulfate
		NO₃^-	nitrate	SiO₃^2-	silicate
		OH^-	hydroxide	C₂^2-	carbide
		CH₃COO^-	acetate	C₂O₄^2-	oxalate
		CrO₂^-	chromite	CrO₄^2-	chromate
		CN^-	cyanide	Cr₂O₇^2-	dichromate
		CNO^-	cyanate	C₄H₄O₆^2-	tartrate
		CNS^-	thiocyanate	MoO₄^2-	molybdate
		O₂^-	superoxide	O₂^2-	peroxide
		MnO₄^-	permanganate	S₂^2-	disulfide
		ClO^-	hypochlorite
		ClO₂^-	chlorite
		ClO₃^-	chlorate
		ClO₄^-	perchlorate
		BrO^-	hypobromite
		BrO₂^-	bromite
		BrO₃^-	bromate
		BrO₄^-	perbromate
		IO^-	hypoiodite
		IO₂^-	iodite
		IO₃^-	iodate
		IO₄^-	periodate
		AlO₂^-	aluminate
		N₃^-	azide

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