CHEM 0012

Foundations of Applied Chemistry

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Ions to learn

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Names of Polyatomic ions and their Charges

In this course, you will need to learn some polyatomic ions. Be sure to learn their names, formulas and their charges.

Cation: ammonium, NH4+
Anions: nitrate, NO3
acetate, C2H3O2
sulfate, SO42-
hydroxide, OH
phosphate, PO43-
carbonate, CO32-
cyanide, CN
chlorate, ClO3
permanganate, MnO4
chromate, CrO42-
dichromate, Cr2O72-

Hint: Make flash cards for learning the ions – on one side, write the formula, on the other side, write the name.

Oxidation Number Rules

  1. The sum of all the Oxidation Number, ON, over all the atoms in a chemical species is equal to the charge on the chemical species
  2. In their compounds, the alkali metals and the alkaline earths have ON of +1 and +2 respectively.
  3. In compounds the ON of fluorine is almost always –1
  4. In compounds, the ON of hydrogen is usually +1
  5. In compounds, the ON of oxygen is usually –2.
  6. In binary (two-element) compounds with metals:
    Group 7A have ON of –1,
    Group 6A have ON of –2 and
    Group 5A have ON of –3.

Whenever two rules appear to contradict one another follow the rule that appears higher on the list.


For Practice Problems click here

The following table summarizes the solubility ionic compounds in water formed with these common anions . Use this as a guide to predict products of chemical reactions for double-replacement reactions.

Nitrates, NO3 ALL
Acetates, C2H3O2 ALL
Chlorides, Cl ALL, except … AgCl, Hg2Cl2, PbCl2
Sulfates, SO42- ALL*, except … BaSO4, SrSO4, PbSO4
Salts of group IA ALL
Salts of ammonium, NH4+ ALL
Acids ALL
Oxides, O2 Group IA,
Group IIA (Ca, Sr, Ba)
Hydroxides, OH Group IA,
Group IIA (Ca*, Sr, Ba)
Sulfides, S2- Group IA, Group IIA, (NH4)2S ALL OTHER
Phosphates, PO43- Group IA, (NH4)3PO4 ALL OTHER
Carbonates, CO32- Group IA, (NH4)2CO3 ALL OTHER

* Ca(OH)2, CaSO4 are moderately soluble.

The following table shows the activity series for some of the more common metals in order of deceasing reactivity, with the most reactive metal at the top of the list. It should not be surprising to you to find the alkali metals at the top of the list and the more unreactive metals at the bottom of the list.

Use this table to predict single replacement reactions.

This is a reference table and will be available to you in examinations. Do not attempt to memorize this table.

Lithium Li  Li+ + e-
Potassium K+ + e-
Barium Ba  Ba2+ + 2 e-
Calcium Ca  Ca2+ + 2 e-
Sodium Na  Na+ + e-
Magnesium Mg  Mg2+ + 2 e-
Aluminum Al  Al3+ + 3 e-
Manganese Mn  Mn2+ + 2 e-
Zinc Zn  Zn2+ + 2 e-
Chromium Cr  Cr3+ + 3 e-
Iron Fe  Fe2+ + 2 e-
Cobalt Co  Co2+ + 2 e-
Nickel Ni  Ni2+ + 2 e-
Tin Sn  Sn2+ + 2 e-
Lead Pb  Pb2+ + 2 e-
Hydrogen H2  2 H+ + 2 e-
Copper Cu  Cu2+ + 2 e-
Silver Ag  Ag+ + e-
Mercury Hg  Hg2+ + 2 e-
Platinum Pt  Pt2+ + 2 e-
Gold Au  Au3+ + 3 e-