Group of the periodic table

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In chemistry, a group of the periodic table is understood to mean any column of the periodic table . All elements of a group have the same number of valence electrons and therefore have similar chemical properties . Groups with particularly similar properties are also referred to as element families ; this mainly concerns the alkali and alkaline earth metals as well as the halogens .

Within each group, the atomic mass and the metallic character of the elements increase from top to bottom , while the electronegativity tends to decrease.

There are a total of 18 groups, of which eight (groups 1, 2 and 13–18) are called main groups and ten (groups 3–12) are called subgroups ; the transition metals are in the subgroups . Several groups are combined into blocks .

Names of the groups

Class group

Because the elements in a group have similar chemical properties , some groups have special names. The best-known groups are in the first and second columns: alkali metals and alkaline earth metals. In the seventh and eighth columns you can find the halogens and noble gases.

CAS convention

Term used by the Chemical Abstracts Service (CAS) until 1986, which refers to the short period system. It is still widespread in Europe today. A stands for main and B for subgroup elements.

IUPAC Convention (old)

The old IUPAC number ( International Union of Pure and Applied Chemistry ) referred to the long-period system. It was common in America; A stood for the left and B for the right side of the periodic table.

IUPAC Convention (current)

The numbering of the groups with Arabic numerals (1 to 18) follows the valid IUPAC convention and should replace the use of the CAS and the old IUPAC conventions.

Comparison table

The groups of the periodic table
IUPAC (current) Group name Main group / sub group CAS IUPAC (old)
Group 1 Alkali metals and hydrogen 1st main group IA IA
Group 2 Alkaline earth metals 2nd main group IIA IIA
Group 3 Scandium group 3rd subgroup IIIB IIIA
Group 4 Titanium group 4th subgroup IVB IVA
Group 5 Vanadium group 5th subgroup VB VA
Group 6 Chromium group 6th subgroup VIB VIA
Group 7 Manganese group 7th subgroup VIIB VIIA
Group 8 Iron group 8th subgroup VIIIB VIIIA
Group 9 Cobalt group 8th subgroup VIIIB VIIIA
Group 10 Nickel group 8th subgroup VIIIB VIIIA
Group 11 Copper group 1st subgroup IB IB
Group 12 Zinc group 2nd subgroup IIB IIB
Group 13 Boron group / earth metals 3rd main group IIIA IIIB
Group 14 Carbon-silicon group / tetrele 4th main group IVA IVB
Group 15 Nitrogen-phosphorus group / pnictogens 5th main group VA VB
Group 16 Chalcogens / oxygen group / ore formers 6th main group VIA VIB
Group 17 Halogens / fluorine groups / salt formers 7th main group VIIA VIIB
Group 18 Noble gases / helium group 8. Main group VIIIA VIIIB

Furthermore, because of their similar chemical properties, the lanthanides and the actinides are often considered as a group. The f-orbital is gradually filled with them.

The not yet found elements with the atomic number 122 to 153 form a group that is called superactinoids after Glenn T. Seaborg . With them the 5g and 6f orbitals are filled. All of these elements are likely to be unstable and radioactive.

See also

Individual evidence

  1. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 91st – 100th, improved and greatly expanded edition. Walter de Gruyter, Berlin 1985, ISBN 3-11-007511-3 , p. 302.
  2. J. Huheey: Inorganic Chemistry. 2nd edition, 1995, ISBN 3-11-013557-4 .