Group (periodic table)

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A group, also known as a family, is a vertical column in the periodic table of the chemical elements. There are 18 groups in the standard periodic table.

It is no accident that several of these correspond directly to chemical series: the periodic table was originally created to organize the known chemical series into a single coherent scheme.

The modern explanation of the pattern of the periodic table is that the elements in a group have similar (conch) configurations of the outermost electron shells of their atoms: as most chemical properties are dominated by outer electron. There are three ways of numbering the groups of the periodic table, one using Hindu-Arabic numerals and the other two using Roman numerals. The Roman numeral names are the original traditional names of the groups; the Arabic numeral names are those recommended by the International Union of Pure and Applied Chemistry (IUPAC) to replace the old names in an attempt to reduce the confusion generated by the two older, but mutually confusing, schemes.

There is considerable confusion surrounding the two old systems in use (old IUPAC and CAS) that combined the use of Roman numerals with letters. In the old IUPAC system the letters A and B were designated to the left (A) and right (B) part of the table, while in the CAS system the letters A and B were designated to main group elements (A) and transition elements (B). The former system was frequently used in Europe while the latter was most common in America. The new IUPAC scheme was developed to replace both systems as they confusingly used the same names to mean different things.

The periodic table groups are as follows (in the brackets are shown the old systems: European and American):

Group 1 (IA,IA): the alkali metals or hydrogen family/lithium family
Group 2 (IIA,IIA): the alkaline earth metals or helium family/beryllium family
Group 3 (IIIA,IIIB): the scandium family
Group 4 (IVA,IVB): the titanium family
Group 5 (VA,VB): the vanadium family
Group 6 (VIA,VIB): the chromium family
Group 7 (VIIA,VIIB): the manganese family
Group 8 (VIII): the iron family
Group 9 (VIII): the cobalt family
Group 10 (VIII): the nickel family
Group 11 (IB,IB): the coinage metals (not an IUPAC-recommended name) or copper family
Group 12 (IIB,IIB): the zinc family
Group 13 (IIIB,IIIA): the boron family
Group 14 (IVB,IVA): the carbon family
Group 15 (VB,VA): the pnictogens (not an IUPAC-recommended name) or nitrogen family
Group 16 (VIB,VIA): the chalcogens or oxygen family
Group 17 (VIIB,VIIA): the halogens or fluorine family
Group 18 (Group 0): the noble gases or helium family/neon family

Note: Wikipedia style should be to replace the old names of the groups with the new IUPAC names throughout, with a historical mention of the old name where appropriate.

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