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Ionic compound with a multivalent metal

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What does multivalent mean?
• Some transition metals are multivalent
• This means they have more than one ion
form
• Look at the periodic table and locate some
multivalent transition metals
• The most common ion is listed first
• What is the most common ion for Cu? , Au?
Page 172
What are multivalent ions?
For Example: Copper has 2 ion forms
Can be a 1+ or 2+ ion
Copper I Chloride
Copper II Chloride
Writing names for multivalent ions
• We need to distinguish between the two or three
different ion forms
• Use roman numerals from I – VII which
corresponds to 1+ - 7+ ion charges
Metal Ion charge
1+
2+
3+
4+
5+
6+
7+
Roman Numeral
I
II
III
IV
V
VI
VII
• For example:
– Nickel can have two ion forms, Ni2+ and Ni3+
– These are named nickel (II) and Nickel (III)
Writing formulas for compounds
containing a multivalent metal
• There will only be 1 multivalent metal in a
compound
• It is the metal so it is first in the name (same as
ionic compounds)
• The roman numeral will indicate which ion form
is in the compound
Steps for writing formulas for
multivalent compounds
• Step 1: Identify each ion and its charge
• Step 2: Determine the total charges
needed to balance positive and negative
• Step 3: Note the ratio of positive ions to
negative ions
• Step 4: Use subscripts to write the
formula, 1’s are not shown in subscript
Try the formula for
titanium (IV) fluoride
ions
Total charge to balance
Ti4+ and F1+4 = -1-1-1-1
ratio
1:4
formula
TiF4
189-191
Lowest Common Multiple-A useful
Trick
Manganese (III) Sulfide
Lowest common multiple for 3 and 2 is 6
ions
Total charge to balance
3+
Mn
and
2S
+3+3 = -2-2-2
ratio
2:3
formula
Mn2S3
Writing formulas for compounds that
contain a multivalent metal
Key Points:
• The metal is always first
• The metal is always the positive ion
• The metal could be a multivalent
metal
• Go to the periodic table and check
Steps for Writing formulas for compounds
that contain a multivalent metal
•
•
•
•
•
Step 1: Identify a multivalent metal
Step 2: identify its different ion forms
Step 3: determine the ratio of ions in the formula
Step 4: what is the charge on the negative ion?
Step 5: Balance the positive and negative
charges
• Step 6: Write the name using roman numerals in
brackets, following the positive ion to indicate
which ion was used
Example: FeI2
• Is there a multivalent metal?
• Yes, Fe, Iron
• What are its different ion forms?
• 3+ and 2+
• What is the ratio of ions
• 1 Fe : 2 I
• What is the charge on the negative ion
• I, Iodine, ion charge is 1• but there are 2 so the total negative charge is
2• Balance the positive and negative charges
• Iron must have a 2+ charge to balance the two
1- charges from Iodine
• Write the name using a roman numeral to say which ion form of Iron
is present
• The negative ion must drop its ending and add
–ide (same as ionic compounds)
• Iron (II) Iodide
Try another example: PbF4
•
•
•
•
•
Pb
2+ and 4+
Pb 1: 4 F
F’s ion charge 1Balance the charges
• 4+ charges to balance the 4 1- charges of F
• Therefore Pb must be the 4+ ion
• Lead (IV) Fluoride
Meet out new class plant!
Video
Homework
to help you practice writing formulas and naming
compounds that contain a multivalent metal
• In workbook p. 68 1-3
Questions to practice writing formulas for
ionic compounds
Text book p. 188
1. a, c, e
2. b, d, f, h, j, l, n
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