Knowledge Assessment
Write the name or formula of each:
1.
2.
3.
4.
5.
6.
7.
Li+
Cr2+
Ag+
O2KBr
Fe2O3
ZnS
8. strontium ion
9. iron (III) ion
10. cadmium ion
11. nitride ion
12. lithium sulfide
13. cobalt (II)
phosphide
14. silver oxide
Polyatomic Ionic Compounds
(or Ternary Ionic Compounds)
See Textbook
Table Page 224
Reference Pages: 254 - 255
Objectives
• Write the names of polyatomic ionic
compounds from their formulas
• Write the chemical formulas of polyatomic
ionic compounds from their names
Classification of Compounds
• Binary Ionic: 2 types of atoms (cation and
anion) IONIC BONDING
• Polyatomic Ionic: (Ternary) 3 or more types of
atoms (cation and anion) IONIC
BONDING
• Binary Molecular: 2 types of atoms (both nonmetals) COVALENT BONDING
• Acids: Contain Hydrogen and often oxygen
USUALLY COVALENT BONDING
Polyatomic Ions
• Groups of atoms that stay
together and have an overall
charge, and one name.
• Usually end in –ate or –ite
Check Your Golden Sheet
• Sulfate: SO42--
Sulfite: SO32—
• Carbonate: CO32—
• Chromate: CrO42–
• Dichromate: Cr2O72—
•
: NH41+
Polyatomic ions are…
•
•
•
•
•
•
Acetate:
Nitrate:
Nitrite:
Permanganate: MnO41Hydroxide: OH1Cyanide: CN1-
To Write the Name of a Compound
Containing a Polyatomic Ion
1.
2.
3.
4.
5.
Write the name of the cation (most likely a metal)
Determine if the cation will need Roman Numerals (is it
a Transition Metal other than Ag, Zn, or Cd?)
Write the parentheses for the Roman Numerals but
don’t fill in just yet
Write the name of the anion (either a non-metal ending
in –ide, or get the name from the Golden Sheet!)
If Roman Numerals are needed, determine the charge
on the cation by the total charge of the anions (either
figure out the charge using your PT or look up the
charge on the Golden Sheet)
Example
Fe2(SiO3)3
1.
2.
3.
4.
5.
Fe is “iron”
Iron is a transition metal and will need Roman
Numerals
iron (
)
SiO3 (on the Golden Sheet) is called “silicate” so now
we have: iron ( ) silicate
The charge on a silicate ion is 2– and there are three
of them in the formula, so the total negative charge is
6– this means that the total positive charge must be
6+. This is distributed over “two” iron atoms, so each
iron atom must have a charge of 3+.
iron (III) silicate
Naming Ternary Ionic
Compounds
• Ca(NO3)2
• Co(C2H3O2)2
• K2SO4
• Fe(CN)2
Writing Formulas for Compounds
with Polyatomic Ions
1. Determine the formulas AND CHARGES
for both the cation and the anion using
the PT or the Golden Sheet
2. Determine how many of each ion you
need in order for the total charges to
balance out
3. Write the formula. Remember to use
parentheses if more than one polyatomic
ion is needed.
Example
aluminum peroxide
1. Aluminum = Al3+ (from PT)
peroxide = O22– (from Golden Sheet)
2. It will take “two” Al3+ ions and “three” O22–
ions to balance the overall charges
3. So…
Al2(O2)3
Formulas of Polyatomic
Compounds
• aluminum acetate
• sodium phosphate
• zinc hydroxide
• ammonium carbonate
• copper (II) nitrite