Name: _________________________________ Date: ______________ Per: __________ #: _______
Polyatomic Ions
-2
Polyatomic ion=
Poly =
Atomic = Carbonate Ion CO3
Ion = Ex) Carbonate ion = CO3 -2 = ___ carbon
atom bonded with ___ oxygen atoms
Common Polyatomic Ions
-1 Charge -2 Charge -3 Charge
Formula Name & Diagram Formula Name & Diagram Formula Name & Diagram
__ __ __
NO2 __________________ SO3 __________________ PO4 __________________
NO3 __
__________________ SO4 __
__________________ +1 Charge
Formula Name & Diagram
__
NH4 __________________
__ __
OH __________________ CO3 __________________
__
ClO3 __________________
__ __
MnO4 Permanganate CrO4 Chromate
__ __
C2H3O2 Acetate Cr2O7 Dichromate
__
HCO3 Bicarbonate
Counting the number of Polyatomic Ions
To count the # of ions:
(NH4)2
To count the # of individual atoms in each ion:
(NH4)2
Practice: 1. (NH4)2 = ______ ions of ammonium 2. (SO4)4 = ______ ions of sulfate
# of N atoms = _____ # of S atoms = _____
# of H atoms = _____ # of O atoms = _____
3. (CO3)3 = ______ ions of carbonate 4. (C2H3O2)4 = ______ ions of acetate
# of C atoms = _____ # of C atoms = _____
# of O atoms = _____ # of H atoms = _____
# of O atoms = _____
Steps for doing Kriss-Kross with Polyatomic Ions:
Ammonium chloride Steps: Ammonium sulfate
1.
2.
3.
Tip: Only use parentheses when more than 1 polyatomic ion is used. Do not write 1’s or charges!
Questions:
1. Looking at the ammonium sulfate example above, what is your total positive charge? What is the
total negative charge? What do you notice about these two numbers?
2. What is the sum of these two numbers? How can you double check that you have correctly written
an ionic formula?
3. What do subscripts represent?
4. Why do you think parentheses are written around the polyatomic ion when more than one ion is
used?
Practice
Cation: Anion:
Write down Write down Show Kriss Kross Formula
ion symbol ion symbol
Example:
Lithium Dichromate Li +1 (Cr2O7) -2
Li2 Cr2O7
Li +1 (Cr2O7) -2 Li2 (Cr2O7)1
1. Ammonium Chlorine
2. Barium Nitrite
3. Potassium Chromate
4. Ammonium Phosphate