2. What are polyatomic ions? n Examples: n CO 3 2- = carbonate. n CO 2 2- = carbonite. n PO 4 3- = phosphate n PO 3 3- = phosphite Polyatomic ions are ions made of 2 or more atoms with a charge for the group. Charge An ion is a particle with a charge.

3. How do we combine these polyatomic ions ? n n Write the positive ion first with its charge n Ca 2+ n Then write the negative ion with its charge NO 3 - Do a cross multiplication Ca 2+ NO 3 1- n Use parenthesis if you have to multiply a polyatomic ion Ca(NO 3 ) 2

4. Let’s see some examples Write the formulas of the compounds formed between: 1)Ammonium and carbonate (NH 4 ) 2 CO 3 2) Potassium and Chlorite KClO 2 3) Aluminum and Sulfite Al 2 (SO 3 ) 3 4) Barium and phosphate Ba 3 (PO 4 ) 2

5. How do we name these compounds? CaSO 4 = Calcium sulfateFeSO 4 = Iron (II) sulfate (NH 4 ) 2 S = Ammonium sulfide (NH 4 ) 2 SO 4 = Ammonium sulfate

6. Let’s practice … write the names of: CaCO 2 Calcium Carbonite Ga(NO 3 ) 3 Gallium Nitrate Fe(ClO) 2 Iron (II) hypochlorite (NH 4 ) 3 PO 4 Ammonium phosphate NH 4 Cl Ammonium chloride

7. More practice Write the formula of: Iron (II) Perchlorate Fe(ClO 4 ) 2 Potassium Nitrate KNO 3 Mercury (I) Sulfite Hg 2 SO 3 Easy?

8. Remember!!! In compounds involving polyatomic ions 1. Consider the polyatomic ion as a unit 2. The charge is for the whole ion 3. Use parenthesis to multiply polyatomic ions When combined with metals use roman numerals if and only if the metal has more than one charge. Remember!!!Remember!!! When naming the polyatomic ion remember to use the correct name for each.

9. You can practice more!!! If you want more practice go to http://dbhs.wvusd.k12.ca.us/Nom enclature/Nomenclature.html