Group (periodic table)

Among a group of the periodic table is meant in chemistry each 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 more similar features are referred to as families element; this concerns mainly the alkali and alkaline earth metals and the halogens.

Within each group increases from top to bottom, the atomic mass and the metallic character of the elements, the electronegativity decreases.

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

Names of the groups

Group Name

Since the elements of a group show similar chemical properties, some groups have special names. The most famous groups are in the first and second columns: alkali metals and alkaline earth metals. In the seventh and eighth column, the halogens and noble gases are found.

CAS Convention

Chemical Abstracts Service (CAS ) to 1986 Applied term which refers to the short-period system. It is common in Europe today still far. A stands for B for the main and sub-group elements.

IUPAC convention ( old)

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

IUPAC convention (current)

The numbering of the groups with Arabic numerals (1 to 18) followed by the valid IUPAC convention and was intended to replace the use of the CAS and the old IUPAC convention.

Comparison Chart

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

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