Binary Ionic Compounds with Multivalent Metals
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Some metals can form more than one type of ion.
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Such metals are called multivalent metals.
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For example, copper can form ions with a 1+ or 2+ charge, as shown on your
periodic chart of ions.
Question: Name some other multivalent metals besides copper.
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Question: Where on the periodic table do you find these multivalent
metals? ________________________________________________
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To distinguish between the ions, a Roman numeral is
written after the name of the metal.
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For example, Cu+ is written as copper (I), pronounced
“copper one.”
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Cu2+ is written as copper (II), pronounced “copper two.”
Chemical Formulas and Names of Ionic Compounds Containing
Multivalent Metals
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To write the chemical formula of a multivalent metal, follow the
same process as for the binary ionic compounds you have been
naming so far.
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The only difference is that you cannot tell the charge on the metal
ion by looking at the periodic table because there will be more
than one choice. Instead, look at the Roman numeral in the name,
which will tell you the charge.
Question: What are the Roman numerals for 8, 9 and 10? _________________
EXAMPLE: The name chromium(III) chloride tells you that the chromium ion in the
compound is Cr3+. The chloride ion is Cl-. For a neutral compound, there must be three
chlorine ions for every one chromium ion, so the formula is CrCl3.
Question:
Write the formulas for:
a) copper(II) chloride
b) lead(IV) iodide
•
When naming a compound that contains a multivalent ion, you must include a
Roman numeral to show which charge the ion has.
•
The charge of the negative ion can help you determine the charge of your positive
ion
Question: Write the chemical names for:
a) NiCl3 _______________________________
b) MnO ______________________________
c) Cu2S _______________________________
Sample Problem: Naming an Ionic Compound with a Multivalent Metal
Problem
The compound Fe2O3 is used as a source of iron in the steel industry and is partly
responsible for the red soil on PEI. What is the name of Fe2O3?
Solution
1. Identify the ions.
• The ion of iron may be either Fe2+ or Fe3+.
• The ion of oxygen is O2-.
2. Determine the ratio of ions in the compound.
• According to the formula, the compound has 2 iron ions for every 3 oxygen ions.
3. The negative charges and the positive charges must be equal in magnitude. Determine
which of the two possible iron ions achieves this balance.
• Since there are 3 oxygen ions, there is an overall negative charge of 6-.
• Since there are 2 iron ions, they must have a charge of 3+ to give an overall
positive charge of 6+.
4. Write the name of the compound using a Roman numeral to indicate the charge of the
metal ion.
• The name of Fe2O3 is iron(III) oxide.
Check Your Solution
• Two Fe3+ ions have a charge of 6+. Three O2- ions have a charge of 6-. The
charges balance.
Practice Problems – Binary Ionic Compounds with Multivalent Metals
1. What is the name of each of the following metal ions?
(a) V4+ _________________________
(b) Ni3+ _________________________
(c) Au+ _________________________
(d) Ti4+ ________________________
2. Write the formula for these compounds with a multivalent metal.
(a) nickel (III) chloride _________________________
(b) lead (IV) sulfide _________________________
(c) copper (I) oxide _________________________
(d) copper (II) oxide _________________________
3. Write the names of the compounds with the following ions.
(a) Co3+ and O2- _________________________
(b) Mn4+ and S2- _________________________
(c) Cu2+ and Cl- _________________________
(d) Cu+ and Cl- _________________________
4. Write the names of the following compounds. Each contains an ion of a multivalent
metal.
(a) FeO _________________________
(b) Cu3N _________________________
(c) SnS2 _________________________
(d) Sn3N2 _________________________
(e) Ni2S3 _________________________
(f) NiS _________________________
(g) PbF4 _________________________
(h) TiS2 _________________________