Worksheet # 4-Calculating Oxidation Numbers The charge an element has in a compound in called an oxidation number. Many elements only have one possible oxidation number, but other elements have several possible oxidation numbers depending upon what they are combined with and the conditions under which they formed. Both metals and nonmetals may have more than one oxidation number. However, we will learn how to determine the oxidation numbers of the metals in a particular compound. Remember that the total charge on any compound is zero. Therefore, if we know the oxidation number of one element in a compound we can figure out the oxidation number of the other element in the compound. Let us first consider the compound with the formula CuCl. We can look on the periodic table and find that the oxidation number of chlorine is -1. We can use this to determine the oxidation of the Cu in CuCl. If the oxidation of Cl is -1 then we know the oxidation number of Cu must be +1. If we add the numbers together we see that they equal 0. This makes the compound neutral. Now lets try some that are a little more challenging. Example: Bi,0, Now we have 2 Bi and 3 O in this compound. We need to establish some steps to help you. 1. Divide the compound in half. 2. Find the charge of the nonmetal (the element on the right) by looking on your periodic table. It is -2. 3. Multiply the charge by the number of atoms. In this case we have 3. So the charge on all of the oxygen atoms in this compound is –2. (-2)(3)=-6 Bi o, 4. If the right side of the compound its-6 so the left side of the compound must be +6 (remember it has to equal 0). 5. Since there are 2 Bi we know that both bismuth combined are equal to +6. But we need to know the oxidation number of one bismuth so we need to divide by the number of atoms in the compound. (+6/2 atoms)=+3 (-2)(3atoms)- -6 Bị 0, For each of the following compounds infer the oxidation number for an individual metal atom. The oxidation number on chlorine is -1 and the oxidation number for oxygen is-2. Formula Calculation Charge of Formula Calculation Charge of Metal Metal NiO -2 X1=-2 Ni O +2+1 =+2 +2 PbO HgCl PbO, W;O, Sno La,O, Sno, Sb,0, U,O,