1. Ionic Compounds using Polyatomic Ions
Chapter 5

2. What is a Polyatomic Ion?
A cluster of atoms (usually nonmetals) that use molecular bonding within the cluster.
More than one atom covalently bonded (sharing electrons) together carrying a charge (the cluster needs to gain or lose electrons to be satisfied).

3. -ates and -ites nitrite NO2-1 sulfite SO3-2 phosphite PO3-3 nitrate
sulfate
SO4-2
phosphate
PO4-3

4. Notable Exceptions NH4+1 ammonium (a positive polyatomic) CN-1 cyanide
hydroxide
OH-1
ferricyanide
Fe(CN)6-3
ferrocyanide
Fe(CN)6-4

5. What if there’s more than two?
hypochlorite
ClO-1
chlorite
ClO2-1
chlorate
ClO3-1
perchlorate
ClO4-1

6. Write the chemical formula for calcium chlorate
Ca+2 ClO3-1
Ca(ClO3)2

7. Write the chemical formula for aluminum carbonate
Al+3 CO3-2
Al2(CO3)3

8. Write the chemical formula for iron (III) dichromate
Fe+3 Cr2O7-2
note that dichromate does not mean two chromates, it is a particular ion
it got its name for the two chromium’s in the ion, not because there will be two of the polyatomic ions in the compound
Fe2(Cr2O7)3

9. Write the chemical formula for nickel(II) nitrite
Ni+2 NO2-1
Note the charge on the nitrite is -1 not 2x-1, the subscript 2 is part of the ion.
Ni(NO2)2

10. Write the chemical formula for gallium cyanide
not GaCN3
you need 3 cyanides to go with the one gallium
Ga(CN)3

11. Write the name for Mn(SO4)2
Manganese(IV) sulfate

12. Write the name for (NH4)3PO4
Ammonium phosphate
ammonium, NH4+1 is one of the few positive polyatomic ions

13. Write the name for Ca2Fe(CN)6
how do you know whether it is ferrocyanide or ferricyanide?
look at the fact that there are 2 Ca+2 ions present
that means that the total cation is +4 and thus the anion must be -4 to match.
calcium ferrocyanide

14. Write the name for AuSCN
gold(I) thiocyanate

15. Write the chemical formula for tin(IV) hydroxide
Sn(OH)4

16. Write the name for CuCO3
copper(II) carbonate

17. Write the chemical formula for copper(I) ferrocyanide
Cu2Fe(CN)6

18. Write the name for CoAs
cobalt(III) arsenide

19. Write the chemical formula for uranium(VI) fluoride
UF6

20. Write the name for cadmium acetate
Cd(C2H3O2)2

21. Write the chemical formula for iron(III) sulfite
Fe2(SO3)3

22. Write the name for Cr(ClO)3
chromium(III) hypochlorite

23. Write the chemical formula for ammonium nitrate
NH4NO3

24. Write the name for Mg(OH)2
magnesium hydroxide

25. Write the chemical formula for K3Fe(CN)6
potassium ferricyanide

26. Write the name for Pb(Cr2O7)2
lead(IV) dichromate

27. It’s all in the name....

28. Mn(SO4)2 Cr(ClO)3 Which formula contains the most number of “atoms?”
11 atoms 7 atoms
Mn(SO4)2
Cr(ClO)3

29. Mn(SO4)2 Cr(ClO)3 Which formula contains the greatest number of ions?
3 ions 4 ions
Mn(SO4)2
Cr(ClO)3

30. Which formula has the highest total charge on the anions?
Mn(SO4)2
Cr(ClO)3

31. Mn(SO4)2 Cr(ClO)3 Which formula has the largest molar mass?
55+2(32)+8(16) 52+3(35.5)+3(16)
= 247 = 206.5
Mn(SO4)2
Cr(ClO)3