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Stock System |
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The stock-naming system is and easy concept to comprehend. Different elements have multiple oxidation states. To find these oxidation numbers it is necessary to either memorize the oxidation numbers or to use an oxidation chart to find the oxidation numbers. Some elements have positive oxidation states and some negative. The stock-naming system though, only deals with the elements that have positive oxidation states. Certain elements like lead (Pb), nickel (Ni), cobalt (Co), and copper (Cu) have multiple oxidation states. They can each have oxidation numbers of 1, 2 and so on. Now, if you have to balance a compound that contains one of these elements, how are you to know what oxidation number the element has. It could be a variety of numbers because this element has a variety of oxidation states. This is where the stock-naming system comes into play. Through the stock-naming system it becomes possible to determine the oxidation number. When dealing with these elements in problems it should be made clear what the oxidation number is. The way it is made clear is by the oxidation number being given. Just after the element there should be parenthesis and inside these parenthesis should be a Roman Numeral. This Roman Numeral indicates the oxidation number of the element. If you have, Cu(II), then you know you have one atom of copper and that its oxidation number is 2. If you had Pb(V) you would have a lead molecule with the oxidation number of 5. What may be confusing to some people is what is an oxidation number. The oxidation number is a representation of how many electrons have been gained or lost by the element. For each electron the element loses the oxidation number increases by one. So Cu(II) has two more protons than electrons, giving it a charge of +2. So if the element were Cu(IV) that would mean that the copper element had lost 4 electrons and had a charge of +4. Without the parenthesis it would be impossible to determine the molecular formula of compounds. Say we are given the compound Iron chloride. Possible answers are FeCl2 or FeCl3. How is that so? The molecular formula could be a variety of things because Iron has multiple oxidation states. When the compound's name is given to us correctly it would read Iron(III) or Iron(II) chloride. Only by using the Roman Numerals are we able to determine the oxidation state of iron. And the only way to determine which chemical formula is the correct one it is required to have the oxidation number of iron. Back to Fordham Prep home page Please forward all questions, comments and criticisms to Gregory L. Curran. |
