Polyatomic Ions - Download as PowerPoint

							Polyatomic Ions
Binary vs. Polyatomic

 So far, we have only been talking about
  binary compounds (compounds made up
  of only 2 different elements).
 Many compounds are polyatomic
  (consisting of more than 2 different
  elements).
 Several common polyatomic ions exist,
  consisting of 2 or more different
  nonmetals joined together by covalent
  bonds.
 The formulas, names and charges of the
  most common ones must be memorized.
 Name       Chemical Formula
ammonium         NH4+
hydroxide         OH–
carbonate        CO32–
 nitrate         NO3–
phosphate        PO43–
 sulfate         SO42–
 chlorate        ClO3-
 acetate        C2H3O2-
Rules for Dealing with Polyatomics

 Treat the polyatomic ion as one ion –
  don’t think about the different elements.
 Most end with “-ate” instead of “-ide”.
 When you need to indicate more than
  one polyatomic, place it in brackets first.
Examples

   Write the formula for potassium hydroxide.

          K+          OH¯
   Use the cross-over method to get the
    formula.
                KOH
Examples

   Write the formula for sodium sulfate.

          Na+            SO42-
   Use the cross-over method to get the
    formula.
                Na2SO4
Examples

   Write the formula for ammonium sulfide.

          NH4+          S2-
   Use the cross-over method to get the
    formula.
              (NH4)2S