Stock System for elements that form
ions having more than one charge
Name______________________________
Date________ Block______
Most of the transition metals and some of the metals in groups 13, 14, 15, and 16 can form ions
with more than one charge. Only zinc and silver have fixed charges. This variation in charge
occurs because the transition metal atoms may use one or more of their d sublevel electrons as a
valence electron, or, as in the case of metals in groups 13-16, sometimes, only the p sublevel
valence electrons are lost.
Naming these ions is easy. The Stock system uses the name of the element and a Roman
numeral representing the size of the charge that is written after the name of the element.
Note: the Roman numeral is NOT used when writing formulas involving these metals.
The following are examples of metals that form ions having more than one charge. Only the
more common charges have been given here (some may form ions having other charges).
Fe+2
Fe+3
iron(II) ion
iron(III) ion
Hg2+2 mercury(I) ion*
Hg+2 mercury(II) ion
Sn+2 tin(II) ion
Sn+4 tin(IV) ion
Cu+1
Cu+2
copper(I) ion
copper(II) ion
Pb+2
Pb+4
lead(II) ion
lead(IV) ion
Cr+2
Cr+3
chromium(II) ion
chromium(III) ion
Mn+2
Mn+3
manganese(II) ion
manganese(III) ion
Co+2
Co+3
cobalt(II) ion
cobalt(III) ion
Cd+2
Cd+3
cadmium(II) ion
cadmium(III) ion
Ti+2
Ti+4
titanium(II) ion
titanium(IV) ion
Bi+3
Bi+5
bismuth(III) ion
bismuth(V) ion
* NOTE: the mercury(I) ion has two atoms covalently bonded that act as a single ion with a
charge of +2 because each atom has lost one valence electron; the mercury(II) ion is a single
mercury atom that has lost its 2 valence electrons and it has a charge of +2.
Naming Compounds Containing Ions That Can Have More Than One Charge:
To name such compounds, simply follow the rule for naming binary ionic compounds: name the
cation first, then name the anion. The only difference is that you MUST include the Roman
numeral for the charge of the cation. Remember that the anions have fixed charges.
Examples:
In the formula MnO, the manganese ion has a +2 charge and the oxide has –2 charge. The
compound is called manganese(II) oxide.
In the formula CuS, the copper ion has a charge of +2 (there is only one copper ion and there is
one sulfide ion with a charge of –2, so the copper ion must have a charge of +2). The compound
is named copper(II) sulfide.
In the formula Cu2S, there are two copper ions and one sulfide ion. Each of the copper ions
must have a charge of +1 to give a total positive charge of +2 to balance the total negative charge
of –2. Therefore, the compound is called copper(I) sulfide.
To write the formula when given the name of a compound, write the symbol for each ion above
its name first. Then write a balanced formula.
Cu+2
S-2
copper(II) sulfide
Fe+3
O-2
iron(III) oxide
CuS
Fe2O3
Cu+1
S-2
copper(I) sulfide
Cu2S
Fe+2 O-2
iron(II) oxide
FeO
Remember: Roman numerals are NOT written in the chemical formula!
For each of the following, write the correct chemical formula:
1. copper(I) oxide _____________
11. iron(III) oxide ____________
2. lead(II) chloride ____________
12. lead(IV) oxide ____________
3. cobalt(II) chloride ___________
13. cobalt(III) chloride __________
4. mercury(II) bromide __________
14. mercury(I) bromide __________
5. mercury(I) oxide __________
15. mercury(II) oxide __________
6. chromium(III) nitride __________
16. chromium(II) nitride _________
7. tin(IV) fluoride __________
17. iron(II) sulfide _________
8. iron(III) oxide ___________
18. cadmium(II) bromide _________
9. tin(IV) oxide ___________
19. manganese(II) fluoride __________
10. manganese(III) chloride __________
20. mercury(I) nitride __________
Write the correct names for each of the following:
1. MnO _____________________________________
2. PbO2 _____________________________________
3. Fe2O3 ____________________________________
4. Cu3P2 _____________________________________
5. SnF2 _____________________________________
6. CuCl _____________________________________
7. PbI2 ______________________________________
8. SnCl4 _____________________________________
9. CrO3 _____________________________________
10. MnO ___________________________________
11. TiO2 ___________________________________
12. BiF5 ______________________________________
13. PbCl4 _____________________________________
14. CrF3 _____________________________________
15. NiBr2 ____________________________________
16. CrO2 ___________________________________
17. Mn2O7 ___________________________________
18. Fe2O3 ___________________________________
19. NiO ____________________________________
20. Mn2O5 ___________________________________