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.
|2||Alakine earth metals|
|8/9/10||Platinum Group Metals|
|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!
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.