BINARY IONIC
COMPOUNDS
Naming and Writing formulas
Ionic Compounds:
• Formed by combining a cation with an anion.
• Held together by an ionic bond
• The attractive force between ions of
opposite charge.
• Crystal lattice structure:
• Repeating ordered pattern of positive and
negative ions
• Represented by a formula unit
• Displays the lowest ratio of ions in the
crystal
• Example: CaCl2
•
Examples of crystal structures
Naming Binary ionic compounds
• Binary = 2 elements (metal w/ one nonmetal)
• Step #1:
• Name the cation first.
• Step #2:
• Name the anion using the –ide ending.
• Example:
• 1) BaF2
• Barium fluoride
• *subscript does not effect the naming
Learning Check
1.Name the following ionic
• Answers:
compounds:
a. NaO
a. Sodium oxide
b. MgI2
b. Magnesium iodide
c. CaBr2
d. Li2S
c. Calcium bromide
d. Lithium sulfide
WRITING FORMULAS
Binary Ionic Formulas
How do we know the Ion’s Charge?
• Group 1 = +1
• Group 2 = +2
• Group 13 metals = +3 (Al, Ga and In)
• Group 15 Nonmetals = -3 (N & P)
• Group 16 Nonmetals = -2
• Group 17 = -1
• For Groups 3 -12 and Sn & Pb:
•
•
•
Roman Numerals equal positive charge*
Example: Iron (III) = Fe+3
Copper (II) = Cu +2
Goal = Balance charges
• The sum of the positive charges must equal the
sum of the negative charges.
• Overall charge equals zero!
• Example:
• Why is calcium chloride’s formula CaCl2 not just
CaCl?
• Ca+2
• Cl-1
• You need 2(-1) chloride ions to balance the 1(+2)
calcium ion.
Writing formulas: Criss-cross Method
•
Write formulas for
ions with charges.
• Cation first, anion
second.
• Criss-Cross charges
making them
subscripts
• Reduce if necessaryAlways need lowest
ratio of ions
• Example:
• Magnesium fluoride
More examples
• Lithium oxide
• Aluminum selenide
• Calcium sulfide
• Iron (III) bromide
Review - Learning Check
• Write the formulas for the following binary
ionic compounds:
1.Manganese (III) oxide
2.Strontium sulfide
3.Calcium iodide
4.Chromium (VI) fluoride
Learning Check Answers
1.Manganese (III) oxide
•
Mn2O3
•2. Strontium sulfide
•
SrS
•3. Calcium iodide
•
CaI2
•4. Chromium (VI) fluoride
•
CrF6
NAMING IONIC COMPOUNDS
WITH TRANSITION METALS
Groups 3 -12 and Sn & Pb
Naming Compounds with Transition
Metals
• A roman numeral must appear in name when
dealing with transition metals and Sn & Pb.
• Work backwards from formula to determine
charge on cation.
Exceptions: Zn+2, Ag+, Cd+2
• Example: NiCl2
Practice Problems: Name the following
compounds
1. Cr2O3
1. Chromium (III) oxide
2. MnS
2. Manganese (II)
sulfide
3. ZnCl2
3. Zinc chloride
4. FeI3
4. Iron (III) iodide