Polyatomic Ions
+
Na
OH
-
Polyatomic ions
A group of atoms covalently bonded together (molecule)
with an overall charge (in other words, has gained or
lost electrons so as a whole it is an ion)
Ammonium
NH4+
+
Hydroxide
OH-
-
Polyatomic ions



Act as a unit
Endings typically –ate or –ite
Parenthesis used in formula if more than
one polyatomic ion in a compound
Counting Atoms/Molecules
Please identify how many atoms/molecules in the
following:
Ca(NO3)2
____ Ca
_____ NO3
(NH4)3PO4
____ NH4 _____ PO4
Na2CO3
____ Na
_____ CO3
Differentiated Activity


Group 1: Bohr models
Group 2: Finish powerpoint
Example
Find BIP and formula for sodium phosphate
Sodium phosphate
Na+ & PO43-
B IP = 3 Na+ & 1 PO43Formula = Na3(PO4)1
= Na3PO4
Find the BIP and formula
1.) Barium phosphite
1.)BIP = 3Ba2+ & 2PO33Formula = Ba3(PO3)2
2.) Calcium nitrate
2.) BIP = 1Ca2+ & 2NO3Formula = Ca(NO3)2
3.) Rubidium chlorate
3.) B IP = 1Rb+ & 1ClO3Formula = RbClO3
Naming - Example
What is the name of the following
compound:
Al(NO3)3
Aluminum nitrate
Name
 NaOH
 NH4CN
 Ba(MnO4)2
Sodium hydroxide
Ammonium cyanide
Barium permanganate
Reflection

Write some simple things that will help
you to remember how to write names and
formulas for compounds with polyatomic
ions
Bond with a classmate
OH-
Mg2+
OH1
BIP: _______ Mg2+ &
2
________
OH-
Formula: Mg(OH)2