Knowledge Assessment Write the name or formula of each: 1.Li + 2.Cr 2+ 3.Ag + 4.O 2- 5.KBr 6.Fe 2 O 3 7.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:

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 non- metals) 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: SO Sulfite: SO 3 2— Carbonate: CO 3 2— Chromate: CrO 4 2– Dichromate: Cr 2 O 7 2— : NH 4 1+

Polyatomic ions are… Acetate: Nitrate: Nitrite: Permanganate: MnO 4 1- Hydroxide: OH 1- Cyanide: CN 1-

To Write the Name of a Compound Containing a Polyatomic Ion 1.Write the name of the cation (most likely a metal) 2.Determine if the cation will need Roman Numerals (is it a Transition Metal other than Ag, Zn, or Cd?) 3.Write the parentheses for the Roman Numerals but don’t fill in just yet 4.Write the name of the anion (either a non-metal ending in –ide, or get the name from the Golden Sheet!) 5.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 Fe 2 (SiO 3 ) 3 1.Fe is “iron” 2.Iron is a transition metal and will need Roman Numerals 3.iron ( ) 4.SiO 3 (on the Golden Sheet) is called “silicate” so now we have: iron ( ) silicate 5.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(NO 3 ) 2 Co(C 2 H 3 O 2 ) 2 K 2 SO 4 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 = Al 3+ (from PT) peroxide = O 2 2– (from Golden Sheet) 2.It will take “two” Al 3+ ions and “three” O 2 2– ions to balance the overall charges 3.So… Al 2 (O 2 ) 3

Formulas of Polyatomic Compounds aluminum acetate sodium phosphate zinc hydroxide ammonium carbonate copper (II) nitrite