CHEMISTRY PART 8 Ionic Compounds with Polyatomic Ions

Polyatomic Ions  An ion made up of 2 or more different atoms.  Covalent (non-ionic) bonds are between the atoms.  The charge belongs to the entire ion.  Names end in “ate” or “ite”.  See the back of your periodic table.

Polyatomic Ions  Examples:  Ammonium (only one with a positive charge) NH 4 1+ The charge is for the entire compound.  Phosphate PO 4 3-  Phosphite PO 3 3-

Formula Writing  Same process as before, but the polyatomic ion must be placed in brackets if it requires a subscript (more than one).

Formula Writing  Example:  Magnesium nitrate  Mg  2+  NO 3  1-  Mg(NO 3 )

Formula Writing  Example:  Iron (II) sulfate  Fe  2+  SO 4  2-  FeSO 4

Formula Writing  Example:  Ammonium sulfide  NH 4 1+ and S 2-  (NH 4 ) 2 S

Formula Writing  Example:  Iron (II) nitrate  Pb 2+ and NO 3 1-  Pb(NO 3 ) 2

Nomenclature 1. Write the name of the metal (cation) If it is a transition metal, follow those rules. 2. Write the name of the polyatomic ion.

Nomenclature  Example:  NaNo 3  Sodium nitrate  Example:  Ca(OH) 2  Calcium hydroxide

Nomenclature  Example:  Fe(OH) 3  Iron must have a 3+ charge  Iron (III) hydroxide 1-

Nomenclature  Example:  CuSO 4  Copper must have a 2+ charge  Copper (II) sulfate 2-

Nomenclature  Example:  (NH 4 ) 2 SO 4  Ammonium sulfate

Practice  Worksheet  Page 127 # 17, 18