Elements that form ions having

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					Stock System for elements that form                     Name______________________________
ions having more than one charge                        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   iron(II) ion           Hg2+2 mercury(I) ion*           Sn+2 tin(II) ion
Fe+3   iron(III) ion          Hg+2 mercury(II) ion            Sn+4 tin(IV) ion

Cu+1   copper(I) ion          Pb+2    lead(II) ion            Cr+2   chromium(II) ion
Cu+2   copper(II) ion         Pb+4    lead(IV) ion            Cr+3   chromium(III) ion

Mn+2   manganese(II) ion      Co+2    cobalt(II) ion          Cd+2   cadmium(II) ion
Mn+3   manganese(III) ion     Co+3    cobalt(III) ion         Cd+3   cadmium(III) ion

Ti+2   titanium(II) ion       Bi+3    bismuth(III) ion
Ti+4   titanium(IV) ion       Bi+5    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.


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                                Cu+1      S-2
     copper(II) sulfide     CuS                    copper(I) sulfide      Cu2S

       Fe+3    O-2                                     Fe+2 O-2
    iron(III) oxide       Fe2O3                     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 ___________________________________

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