Compounds With Polyatomic Ions
 Are ionic compounds made with a metal ion and a polyatomic (many atom) non-metal
ion.
 There are several to memorize in addition to those containing oxygen which are known
as oxyanions.
 There are 7 main oxyanions
NO31ClO31BrO31IO31-
nitrate
chlorate
bromate
iodate
CO32SO42-
carbonate
sulfate
PO43
phosphate
 Each main oxyanion (“ate”) has derivatives based on the # of oxygens in the formula
 Prefixes and suffixes relate to the main oxyanion.
 Only the # of oxygens change, not the charge.
Change
1 “O” more
MAIN
1 “O” less
2 “O”s less
Name
per…ate
…ate
…ite
hypo…ite
SO52SO42SO32SO22-
Creating the Name:
Example
persulfate
sulfate
sulfite
hyposulfite
eg. Fe(NO3)3
1. metal name unchanged
iron
2. Find the charge on the metal using reverse crossover
Fe?+ (NO3)31Fe3+ (NO3)31iron (III)
iron (III) nitrate
3. Add the metal’s charge using (I, II, III, IV, V, VI).
4. polyatomic ion name
eg.
Na2CO2
Pb(ClO)2
sodium carbonite
lead (II) hypochlorite
Creating the Formula:
1. Write each element’s or ion’s symbol and
charge. Bracket the ion keeping it as a unit.
2. Crossover and simplify when needed.
eg. calcium phosphate
Ca 2+ (PO4) 3Ca3 (PO4)2
Ca3(PO4)2
eg.
eg.
copper (II) sulfite
Cu 2+ (SO3) 2- => Cu2 (SO3)2 => CuSO3
sodium chromate (not an oxyanion)
Na1+ (CrO4)2- => Na2 (CrO4)1 => Na2CrO4
Hydrates
 Are ionic compounds that form crystals containing water molecules within the crystal
structure
Formula
 Ionic compound 1st then a “dot” and finally the number of H2O molecules in the crystal
unit.
eg.
LiCl • 4 H2O
Name
 1st the ionic compound name
 Then “hydrate” which includes a prefix for the number of water molecules.
 Same prefixes as covalent compounds.
eg. MgSO4 • 7 H2O
magnesium sulfate heptahydrate
eg. copper (II) chloride dihydrate
CuCl2 • 2 H2O