Periodic Table groups
In the standard form of the periodic table the s-block, p-block, and d-block elements are organised into 18 vertical columns called groups. These are labelled from 1 to 18 under current IUPAC numenclature.
Earlier labelling schemes (Trivial Group names)
For historical reasons some Groups have special names. Terms such as the "alkali metals" are in very common use whereas the term "pnictogens" is very much less common. Some of these special names are listed in the Table.
| Group | Name |
|---|---|
| 1 | Alkali metals |
| 2 | Alakine earth metals |
| 8/9/10 | Platinum Group Metals |
| 11 | Coinage Metals |
| 15 | Pnictogens |
| 16 | Chalcogens |
| 17 | Halogens |
| 18 | Noble Gases, Inert Gases |
In addition the elements 57-71 (lanthanum-lutetium) are referred to as the lanthanoids (lanthanides) and the elements 89-103 (actinium-lawrencium) are referred to as the actinoids (actinides). The elements Sc, Y, and the lanthanoids are sometimes referred to as the rare earths.
The s-, p-, and d-blocks contain a total of 18 groups. The latest recommendations from IUPAC (the International Union of Pure and Applied Chemistry) require that these be labelled 1 - 18 from left to right. This is a good recommendation in the sense that it is at least unambiguous.
Confusion in labelling schemes
There are two other ways of labelling the groups, and both use labels 1-8 (often in Roman numeral format) with further A and B labels. Unfortunately there is enormous confusion here. The two schemes are shown in the table below, underneath the new IUPAC scheme in the first row. It is easy to see the origins of the confusion!
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1A | 2A | 3A | 4A | 5A | 6A | 7A | 8 | 1B | 2B | 3B | 4B | 5B | 6B | 7B | 0 | ||
| 1A | 2A | 3B | 4B | 5B | 6B | 7B | 8 | 1B | 2B | 3A | 4A | 5A | 6A | 7A | 0 | ||
One of these systems is more common in America and the other in Europe but there is really only room for one convention on a small planet, which is where the IUPAC systems scores. These days most new books are printed with the IUPAC labels, but often one of the older conventions is given as well.
The point about confusion is important. If you really must use one of the two older formats, then you must define which you are using. Otherwise it's not clear whether Group 3B refers to the boron group or to the scandium group.
"In addition the elements
"In addition the elements 57-71 (lanthanum-lutetium) are referred to as the actinoids (actinides) and the elements 89-103 (actinium-lawrencium) are referred to as the actinoids (actinides)."
Small error in the above text: The first group is the lanthanoids (lanthanides).
Thanks, fixed -- WebElements
Thanks, fixed
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Though many will disagree,
Though many will disagree, the IUPAC system of group numbers is much less intuitive than the most recent American scheme, where the representative elements are grouped as A (IA, IIA, etc) and the transition elements are grouped at B, as, in essence, the IUPAC scheme merely numbers the columns. As I attempt to teach chemistry foundations to eighth graders, main focus is on the representative elements; as a result, it is easy for students to remember that all alkali metals have only one valence electron because they are in Group IA, whilst the halogens have seven valence electrons, as they are in Group VIIA. Figuring ion charges and oxidation numbers are also simplified, as Groups IA and IIA form cations with charges +1 and +2, respectively, while figuring out the charge of the anions of the nonmetals is merely taking the group number minus 8--for example, the halogens will usually form anions with a charge of 7-8 = -1. Many higher level chemistry teachers look down at this approach and are willing to point out that there are lots of exceptions, and that simplification of the concepts of chemistry is compromising--I have had plenty of debates with such individuals--but these folks forget that I am teaching 12 and 13-year olds, not college students. Having taught IB Chemistry in the past, I have found that most students find the IUPAC scheme confusing; it is much more important that students learn the secrets of the periodic table as simply as possible, then let them learn the more complex concepts as they move up the academic ladder. (This is why I wish that there was a WebElements printable periodic table with the American system specifically for lower level students.
Thanks for the comment. One
Thanks for the comment. One problem is the "American" A/B system is different to the "European" A/B system, which was one of the reasons IUPAC went for 1-18 in the first place.
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