Naming Binary Compounds
Rules:
1. Determine which element is the cation. The cations are usually found toward the left of
the periodic table and are written first in the name and formula of a molecule.
2. Determine which element is the anion. The anions are non-metals (or hydrogen), located
on the right side of the periodic table, and are written second in the name and formula of
a molecule.
3. Write the cation first using the name of the element.
4. Write the anion second, dropping the usual ending and replacing it with “ide”.
element
fluorine
chlorine
bromine
iodine
hydrogen
anion
fluoride
chloride
bromide
iodide
hydride
element
oxygen
sulphur
nitrogen
phosphorous
carbon
anion
oxide
sulphide
nitride
phosphide
carbide
eg. KCl = potassium chloride
Write the correct chemical name for each of the following:
1. MgO
magnesium oxide
11. K2S
potassium sulphide
2. LiF
lithium fluoride
12. Na2O
sodium oxide
3. NaBr
sodium bromide
13. K2O
potassium oxide
4. CaO
calcium oxide
14. Ca3P2
calcium phosphide
5. AlN
aluminum nitride
15. H2O
hydrogen oxide
6. NaI
sodium iodide
16. CaBr2
calcium bromide
7. Al2S3
aluminum sulphide
17. MgS
magnesium sulphide
8. Ag3P
silver phosphide
18. ZnBr2
zinc bromide
9. BaCl2
barium chloride
19. B2O3
boron oxide
10. AlCl3
aluminum chloride
20. Ba2C
barium carbide
Writing Chemical Formulae
Rules:
1. Write the chemical symbol for the cation first, followed by the symbol of the anion.
2. Write the charge of each ion above each symbol.
3. Cross the charges, ignoring the signs.
4. Reduce the numbers if there is a common factor.
5. If the number beside an element is 1, do not write it.
(The total positive charge will now equal the total negative charge in the molecule.)
Example: silicon oxide
Rule 1
Si
O
Rule 2
Si+4
O-2
Rule 3
Si2O4
Rule 4
SiO2
Write the correct chemical formula for each of the following:
1. sodium nitride
Na3N
11. calcium phosphide
Ca3P2
2. sodium oxide
Na2O
12. sodium fluoride
NaF
3. calcium chloride
CaCl2
13. boron nitride
BN
4. magnesium sulphide
MgS
14. calcium hydride
CaH2
5. silicon oxide
SiO2
15. hydrogen oxide
H2O
6. aluminum carbide
Al4C3
16. aluminum nitride
AlN
7. boron fluoride
BF3
17. potassium carbide
K4C
8. potassium nitride
K3N
18. zinc iodide
ZnI2
9. cesium oxide
Cs2O
19. barium bromide
BaBr2
10. aluminum bromide
AlBr3
20. silver selenide
Ag2Se
Prefix Method
This method is commonly used only for naming binary compounds composed of two non-metals.
Rules:
1. A prefix is used to indicate the number of atoms in the molecule.
number of
atoms
1
2
3
4
5
number of
atoms
6
7
8
9
10
prefix
mono
di
tri
tetra
penta
prefix
hexa
hepta
octa
nona
deca
2. Place the appropriate prefix in front of the cation (mono is dropped in the first element).
3. Place the appropriate prefix in front of the anion, using the “ide” suffix as before.
Exceptions:
1. Peroxides – contain O2-2 ion
Peroxides have an extra oxygen atom. Write the formula for the ordinary oxide and add
one additional oxygen atom. Peroxides are NOT reduced.
barium oxide – BaO
barium peroxide – BaO2
hydrogen oxide – H2O
hydrogen peroxide – H2O2
2. Diatomic Elements
The following gaseous elements consist of two atoms joined together. They do not occur
naturally as a single atom. (mnemonic – HOFBrINCl or Hey NO halogens)
H2 N2 O2 F2 Cl2 Br2 I2
1. sulphur dioxide
SO2
2. carbon disulphide
CS2
3. nitrogen trichloride
NCl3
4. phosphorous pentabromide
PBr5
5. diiodine pentasulphide
I2S5
6. selenium tetrachloride
SeCl4
7. bromine heptafluoride
BrF7
8. nitrogen monoxide
NO
9. selenium trioxide
SeO3
10. dinitrogen trisulphide
N2S3
Compound Ions
Many ions consist of more than one element. These ions all have special names
which you will not need to memorize. A chart of the compound ions will be provided
to you for all tests and quizzes.
The charge given in the chart is the charge on the compound ion as a unit.
Compound molecules are named using the IUPAC system, the only difference being
that if more than one of the compound ions is needed to form a neutral molecule,
brackets are placed around the ion.
nitrate
NO3-1
carbonate
CO3-2
fluorate
FO3-1
sulphate
SO4-2
chlorate
ClO3-1
phosphate
PO4-3
bromate
BrO3-1
hydrogen carbonate
HCO3-1
iodate
IO3-1
hydrogen sulphate
HSO4-1
hydroxide
OH-1
monohydrogen phosphate
HPO4-2
ammonium
NH4+1
dihydrogen phosphate
H2PO4-1
eg. aluminum sulphate =
Al+3
SO4-2
Al2(SO4)3
Complete the following table.
1. silver carbonate
Ag2CO3
11. Al(NO3)3
aluminum nitrate
2. calcium nitrate
Ca(NO3)2
12. LiClO3
lithium chlorate
3. boron bromate
B(BrO3)3
13. Zn(HCO3)2
zinc hydrogen carbonate
4. ammonium chloride
NH4Cl
14. KFO3
potassium fluorate
5. magnesium iodate
Mg(IO3)2
15. C(BrO3)4
carbon (IV) bromate
6. potassium phosphate
K3PO4
16. Ca3(PO4)2
calcium phosphate
7. lithium hydrogen carbonate LiHCO3
17. (NH4)2SO4
ammonium sulphate
8. silicon sulphate
Si(SO4)2
18. Be(OH)2
beryllium hydroxide
9. sodium dihydrogen
phosphate
NaH2PO4
19. Si(IO3)4
silicon (IV) iodate
10. aluminum hydroxide
Al(OH)3
20. Si(CO3)2
silicon (IV) carbonate
Simple Nomenclature
molecul
e
molecular name
1. silicon oxide
SiO2
21. MgCl2
magnesium chloride
2. boron fluoride
BF3
22. SiC
silicon (IV) carbide
3. aluminum carbide
Al4C3
23. Al2S3
aluminum sulphide
4. potassium nitride
K3N
24. SiH4
silicon (IV) hydride
5. cesium oxide
Cs2O
25. H2S
hydrogen sulphide
6. aluminum bromide
AlBr3
26. Ag3P
silver phosphide
7. calcium phosphide
Ca3P2
27. H2O
hydrogen oxide
8. sodium fluoride
NaF
28. MgO
magnesium oxide
9. boron nitride
BN
29. CaH2
calcium hydride
10. nitrogen hydride
NH3
30. NaBr
sodium bromide
11. hydrogen oxide
H2O
31. KF
potassium fluoride
12. calcium nitride
Ca3N2
32. C3N4
carbon (IV) nitride
13. aluminum nitride
AlN
33. H2S
hydrogen sulphide
14. calcium oxide
CaO
34. B2S3
boron sulphide
15. potassium sulphide
K2S
35. BaO
barium oxide
16. zinc oxide
ZnO
36. ZnO
zinc oxide
17. silver nitride
Ag3N
37. SrS
strontium sulphide
18. lithium fluoride
LiF
38. BeS
beryllium sulphide
19. magnesium iodide
MgI2
39. SiCl4
silicon (IV) chloride
20. hydrogen arsenide
H3As
40. AlF3
aluminum fluoride
Compound Ion Nomenclature
1. copper (II) nitrate
Cu(NO3)2
21. K2CO3
potassium carbonate
2. ferrous sulphate
FeSO4
22. Na2SO4
sodium sulphate
3. potassium chlorate
KClO3
23. Zn3(PO4)2
zinc phosphate
4. zinc carbonate
ZnCO3
24. Hg2SO4
mercury (I) sulphate
5. silver phosphate
Ag3PO4
25. Ba(NO3)2
barium nitrate
6. sodium sulphate
Na2SO4
26. Fe(HSO4)3
iron (III) hydrogen sulphate
7. barium hydroxide
Ba(OH)2
27. Pb3(PO4)4
lead (IV) phosphate
8. ammonium phosphate
(NH4)3PO4
28. Hg(NO3)2
mercury (II) nitrate
9.
Pb(HCO3)2
29. FeSO4
iron (II) sulphate
10. cuprous nitrate
CuNO3
30. Sb(HCO3)5 antimony (V) hydrogen carbonate
11. mercury (II) hydrogen sulphate
Hg(HSO4)2
31. MgSO4
magnesium sulphate
12. zinc sulphate
ZnSO4
32. Ag3PO4
silver phosphate
13. auric phosphate
AuPO4
33. NH4NO3
ammonium nitrate
14. aluminum nitrate
Al(NO3)3
34. Sn(OH)4
tin (IV) hydroxide
15. ammonium hydroxide
NH4OH
35. BPO4
boron phosphate
16. boron carbonate
B2(CO3)3
36. Be(OH)2
beryllium hydroxide
17. lead (IV) hydrogen carbonate
Pb(HCO3)4
37. AuHSO4
gold (I) hydrogen sulphate
18. ammonium sulphide
(NH4)2S
38. Cu3(PO4)2
copper (II) phosphate
19. mercuric phosphate
Hg3(PO4)2
39. AgHCO3
silver hydrogen carbonate
20. stibbous carbonate
Sb2(CO3)3
40. Li2SO4
lithium sulphate
plumbous hydrogen carbonate