polyatomic ion

Polyatomic ions form part of the language, or nomenclature of chemistry. We name these groups of atoms so because of their high tendencies to stick together and behave as one.

Common polyatomic ions, in order of electrovalence, then in pseudo-alphabetical order, with related ions adjacent:

• Cations with +1 charge
  • Ammonium: NH₄⁺
  • Hydronium: H₃O⁺
• Anions with -1 charge
  • Acetate: CH₃COO^-
  • Aluminate: AlO₂^-
  • Bromate: BrO₃^-
  • Perchlorate: ClO₄^-
  • Chlorate: ClO₃^-
  • Chlorite: ClO₂^-
  • Hypochlorite: ClO^-
  • Chromite: CrO₂^-
  • Hydrogen Carbonate: HCO₃^-
  • Cyanide: CN^-
  • Thiocyanate: SCN^-
  • Iodate: IO₃^-
  • Dihydrogen Phosphate: H₂PO₄^-
  • Hydrogen Sulphate: HSO₄^-
  • Hydrogen Sulphite: HSO₃^-
  • Hydroxide: OH^-
  • Nitrate: NO₃^-
  • Nitrite: NO₂^-
  • Permanganate: MnO₄^-
• Anions with -2 charge
  • Carbonate: CO₃^2-
  • Chromate: CrO₄^2-
  • Dichromate: Cr₂O₇2^-
  • Molybdate: MoO₄^2-
  • Oxalate: C₂O₄^2-
  • Peroxide: O₂^2-
  • Hydrogen Phosphate: HPO₄^2-
  • Silicate: SiO₃^2-
  • Sulphate: SO₄^2-
  • Sulphite: SO₃^2-
  • Tartrate: C₄H₄O₆^2-
  • Thiosulphate: S₂O₃^2-
• Anions with -3 charge
  • Arsenate: AsO₄^3-
  • Arsenite: AsO₃^3-
  • Ferricyanide: Fe(CN)₆^3-
  • Phosphate: PO₄^3-
  • Phosphite: PO₃^3-
• Anions with -4 charge
  • Ferrocyanide: Fe(CN)₆^4-

Now, I'm not sure how anyone memorizes these, but the following pattern may help. For almost any infix X, the number of oxygen atoms in the molecule decreases one by one, creating this order of names:

perXate
Xate
Xite
hypoXite

I would appreciate any advice from people who actually know chemistry well; it's not my field.

Sources:
http://www2.austin.cc.tx.us/rvsmthsc/chem/chem-Some.html
http://www.chemistry.wustl.edu/EduDev/LabTutorials/PeriodicProperties/Ions/ions.html
http://scidiv.bcc.ctc.edu/wv/4/0004-009-Polyatomicions.html
http://home.earthlink.net/~ssbeaton/addlinfo/polyions.html