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Alternate Group DesignationsThis particular arrangement or designation of the group numbers is used primarily in the United States and most of the textbooks that have been written in the U.S. over the past several decades have used this group designation. I will call it the "Standard American Designation". Internationally, a different designation is used. That different designation is often used in commercially prepared periodic tables and you should become familiar with it.. I will call it the "International Designation." The international designation puts all of the "a" groups on the left side of the table and all of the "b" groups on the right side. I want you to write in the international group numbers above the American group numbers on the periodic table in example 1 so that you will have them for reference. The international designation starts out with Ia then IIa (same as the American) then group IIIb in the U.S. system is called group IIIa, then IVa, then Va, then VIa, then VIIa, then VIII. Then we have Ib (which is the same), IIb (the same), then IIIb, IVb, Vb, VIb, VIIb and O for the inert gases. If you think about the older short form of the periodic table being pulled apart to create the long form, those elements pulled left got the international "a" designation and those that were pulled right got the international "b" designation. As for the American approach, those elements that best matched the family characteristics got the "a" designation and those elements that ended up in the middle of the table got the "b" designation. Incidentally, there is a movement afoot to come up with still another way of designating the elements, which I will call the "New Designation." It has some merit because it gets rid of the a's and b's and group VIII becomes three groups. That method is to simply number the groups from 1 to 18 all the way across the periodic table. You should also write that on example 1 so that you will have it for reference. Other designations have also been proposed and the matter is not yet fully resolved.
The international designation has the advantage of having all the "a" groups on the left side of the periodic table and all the "b" groups on the right side of the periodic table. The American designation has the advantage of having all the "a" groups being the representative elements and all the "b" groups being the transition elements. I think that has a little bit more validity and so that's the way we will do it in this course. The new designation has the advantage of not having any "a" groups or "b" groups. We will use the Standard American Designation. However, you should realize that the properties of the elements are dependent on their location in the periodic table rather than on what numbers and letters are used to designate them. That is really the important thing. After this lesson, you should be able to look at where oxygen is on the periodic table and talk about the properties of oxygen based on that location on the periodic table. Whether you say it is in group VIa or group VIb or group 16 really doesn't matter. Except for purposes of convenience or identification, you should be able to ignore the group designations. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Distance Learning questions Clackamas Community College |
