Ch. 15 and 6 Polyatomic Ions

Polyatomic Ions Tightly bound groups of atoms that behave as a unit and carry a charge. Examples: Ammonium NH4+ Cyanide CN- Sulfite SO32-

Common Polyatomic Ions with a -1 charge ClO-1 hypochlorite ClO2-1 chlorite ClO3-1 chlorate ClO4-1 perchlorate CN-1 cyanide MnO4-1 permanganate NO3-1 nitrate NO2-1 nitrite

-1 polyatomic ions cont. OH-1 hydroxide HCOO-1 formate HCO3-1 hydrogen carbonate HSO3-1 hydrogen sulfite HSO4-1 hydrogen sulfate CH3COO-1 or C2H3O2-1 acetate

-2 polyatomic ions C2O4-2 oxalate CO3-2 carbonate Cr2O7-2 dichromate CrO4-2 chromate SO4-2 sulfate SO3-2 sulfite

-3 polyatomic ion PO4-3 phosphate PO3-3 phosphite

+1 polyatomic ions NH4+1 ammonium H3O+1 hydronium

Polyatomic Ions SO42- Sulfate Examine Relationships Most end in –ite / -ate Trick to remember: The bigger number ate the little number! SO42- Sulfate SO32- Sulfite

The big number ate the little number! NO3- Nitrate NO2- Nitrite PO43- Phosphate PO33- Phosphite

Writing Formulas for Ternary Ionic Compounds A. Contain a polyatomic ion B. Same rules as for binary ionic compounds. One addition – Use parenthesis if there is more than one polyatomic ion Examples: Calcium Hydroxide Calcium - Ca2+ OH- –Hydroxide Formula for compound – Ca(OH)2

Magnesium Dichromate Mg+2 Cr2O7-2 Mg2(Cr2O7)2 MgCr2O7 Boron acetate B3+ C2H3O2-1 B(C2H3O2)3 Magnesium Dichromate Mg+2 Cr2O7-2 Mg2(Cr2O7)2 MgCr2O7 11

Examples (cont.) Magnesium Nitrate Magnesium – Mg2+ Nitrate - ???? Write the formula for the compound

Practice Problems Write formulas for the following ternary ionic compounds: Calcium Carbonate Potassium Sulfate Barium Nitrite Magnesium Phosphate CaCO3 K2SO4 Ba(NO2)2 Mg3 (PO4)2

Naming Ternary Ionic Compounds Same rules as for naming binary ionic compounds: Name the cation – Use a Roman numeral if necessary Name the anion Do not use the word “ion” in the compound name

Practice Problems: Name the following ternary ionic compounds: NaCN KClO Li2SO3 CaC2O4 Al(OH)3 Sn3(PO4)2 Sodium cyanide Potassium hypochlorite Lithium sulfite Calcium oxalate Aluminum hydroxide Tin (II) phosphate

Ionic Compounds- Polyatomic Ions Due at the end of class, Completed OH SO4 PO4 NO3 Zn+2 NH4 K Ca Fe+3 -1 -1 -2 -3 -1 + + +2