Lesson 22

Isn't It Ionic

Polyatomic Ions

Polyatomic ion - an ion composed of a group of atoms with an overall positive or negative charge; most are anions

Polyatomic ion      Name

      OH-1            Hydroxide

     NO3-1            Nitrate

     CO3-2          Carbonate

     SO4-2           Sulfate

    NH4+1        Ammonium

     PO4-3         Phosphate

A good way to realize something is a polyatomic ion is if the name of it ends with -ate. Obviously this isn't true of all of them but for most.

A poly atomic ion still needs electrons to fill its shells and so the poly atomic ion as a group of two elements still needs to combine with another element to become full. This means the zero charge rule still applies.

ex: Nitrate has 1 nitrogen atom and 3 oxygen atoms together. Since nitrogen has 5 valence electrons and oxygen has (6x3) 18, that means that the Oxygen atoms get the 5 electrons from the Nitrogen. 18 + 5 is still only 23 which means that the charge is -1 and Ned's to combine with a metal to gain another electron.

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