1. Polyatomic Ions
A polyatomic ion is an ion which is composed of more than one type of atom joined together in covalent bonds. They are very important in organic chemistry!
Sulfate SO42-

2. Ex. Carbonate, CO32-
Combines with calcium to make shells, corals, rock, etc…
Ex. Cyanide, CN-
A deadly poison to humans!
Ex. Acetate, CH3COO-
Vinegar!!!

3. Each polyatomic ion has its own specially assigned name. (No “ide”)
No need to memorize them! Just use a table on p.192 in your textbook.

4. When writing chemical formulas, treat the polyatomic ion as one ion.
If there is more than one, use brackets!
Ex. Potassium nitrate
K+1 and NO3-1 = KNO3
Ex. Calcium nitrate
Ca+2 and NO3-1 = Ca(NO3)2
Ex. Radium hydroxide
Ra+2 and OH = Ra(OH)2

5. You Try!
Hint: Chemical name ~ If it does not end in “ide” it’s a polyatomic ion!
Chemical formula ~ If it has more than two elements, it’s a polyatomic ion!
Calcium sulfite
Aluminum hydroxide
NH4Cl

6. You Try!
Hint: Chemical name ~ If it does not end in “ide” it’s a polyatomic ion!
Chemical formula ~ If it has more than two elements, it’s a polyatomic ion!
Calcium sulfite = CaSO3
Aluminum hydroxide = Al(OH)3
NH4Cl = Ammonium chloride