Group numbers and names

In the periodic table the numbering of groups has a confused history reflecting developments in presenting and understanding the table itself. In the nomenclature that is used in this book, groups are numbered from 1 to 18, with the lanthanides and actinides all subsumed into group 3. Older numberings based on 1-8 are yet found with a division into A and B subgroups that unfortunately different as per the continent. The s- and early d-block elements are numbered 1A-8A (the last encompassing modern group numbers 8, 9 and 10) in the UK, followed by numbers 1B (now 11) to 8B. In the USA, 1A-8A consider to main groups, with the d-block elements numbered B. This confusion is determined by the newer system.

Some groups of elements are typically given names. Group 1 elements (not hydrogen) are called alkali metals and those of group 2 alkaline earths. The 17 and 18 Groups are the halogens and noble gases, correspondingly. Sometimes group 16 are called chalcogens even though this generally prohibits the first element oxygen: so the term chalcogenide refers to compounds with sulphur, tellurium and selenium. Lanthanides were earlier called rare earths; even though the term is no longer used by chemists it is still general in geochemistry (where it frequently includes yttrium in group 3 in the previous period not a lanthanide but chemically very identical).