Group of the periodic table

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

• Atomic model
• Period of the periodic table

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 .