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In the periodic table of the elements, each numbered column is a group.

In chemistry, a group (also known as a family^[1]) is a column of elements in the periodic table of the chemical elements. There are 18 numbered groups in the periodic table, and the f-block columns (between groups 3 and 4) are not numbered. The elements in a group have similar physical or chemical characteristics of the outermost electron shells of their atoms (i.e., the same core charge), as most chemical properties are dominated by the orbital location of the outermost electron.
There are three systems of group numbering. The modern numbering group 1 to group 18 is recommended by the International Union of Pure and Applied Chemistry (IUPAC). It replaces two older naming schemes that were mutually confusing. Also, groups may be identified by their topmost element or have a specific name. For example, group 16 is variously described as the oxygen group and as the chalcogens.

Group names

In history, several sets of group names have been used:^[2]^[3]

Groups in the Periodic table

IUPAC group	1	2	3^a	^a	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18
Mendeleev (I–VIII)	IA	IIA	IIIB		IVB	VB	VIB	VIIB	VIIIB			IB	IIB	IIIB	IVB	VB	VIB	VIIB	^b
CAS (US, A-B-A)	IA	IIA	IIIB		IVB	VB	VIB	VIIB	VIIIB			IB	IIB	IIIA	IVA	VA	VIA	VIIA	VIIIA
old IUPAC (Europe, A-B)	IA	IIA	IIIA		IVA	VA	VIA	VIIA	VIIIB			IB	IIB	IIIB	IVB	VB	VIB	VIIB	0
Trivial name	Alkali metals	Alkaline earth metals^r										Coinage metals		Triels	Tetrels	Pnictogens^r	Chalcogens^r	Halogens^r	Noble gases^r
Name by element^r	Lithium group	Beryllium group	Scandium group		Titanium group	Vanadium group	Chromium group	Manganese group	Iron group	Cobalt group	Nickel group	Copper group	Zinc group	Boron group	Carbon group	Nitrogen group	Oxygen group	Fluorine group	Helium or Neon group
Period 1	^h H ^h																		He
Period 2	Li	Be												B	C	N	O	F	Ne
Period 3	Na	Mg												Al	Si	P	S	Cl	Ar
Period 4	K	Ca	Sc		Ti	V	Cr	Mn	Fe	Co	Ni	Cu	Zn	Ga	Ge	As	Se	Br	Kr
Period 5	Rb	Sr	Y		Zr	Nb	Mo	Tc	Ru	Rh	Pd	Ag	Cd	In	Sn	Sb	Te	I	Xe
Period 6	Cs	Ba	La	Ce–Lu	Hf	Ta	W	Re	Os	Ir	Pt	Au	Hg	Tl	Pb	Bi	Po	At	Rn
Period 7	Fr	Ra	Ac	Th–Lr	Rf	Db	Sg	Bh	Hs	Mt	Ds	Rg	Cn	Nh	Fl	Mc	Lv	Ts	Og

^a Group 3 has scandium (Sc) and yttrium (Y). For the rest of the group, sources differ as either being (1) lutetium (Lu) and lawrencium (Lr), or (2) lanthanum (La) and actinium (Ac), or (3) the whole set of 15+15 lanthanides and actinides. IUPAC has initiated a project to standardize the definition as either (1) Sc, Y, La and Ac, or (2) Sc, Y, Lu and Lr.^[4]
^b Group 18, the noble gases, were not discovered at the time of Mendeleev's original table. Later (1902), Mendeleev accepted the evidence for their existence, and they could be placed in a new "group 0", consistently and without breaking the periodic table principle.
^r Group name as recommended by IUPAC.
^h Hydrogen (H), while placed in group 1, is not considered to be part of the alkali metals.

New IUPAC names	Old IUPAC .mw-parser-output .nobold{font-weight:normal} (Europe)	CAS (U.S.)	Name by element	Trivial name (*=IUPAC recommended name)	note
Group 1	IA	IA	lithium family	alkali metals*
Group 2	IIA	IIA	beryllium family	alkaline earth metals*
Group 3	IIIA	IIIB	scandium family		Consisting of rare earth elements plus actinides
Group 4	IVA	IVB	titanium family
Group 5	VA	VB	vanadium family
Group 6	VIA	VIB	chromium family
Group 7	VIIA	VIIB	manganese family
Group 8	VIII	VIIIB	iron family
Group 9	VIII	VIIIB	cobalt family
Group 10	VIII	VIIIB	nickel family
Group 11	IB	IB	copper family	coinage metals
Group 12	IIB	IIB	zinc family
Group 13	IIIB	IIIA	boron family	triels	triels from Greek tri (three, III)
Group 14	IVB	IVA	carbon family	tetrels	tetrels from Greek tetra (four, IV)
Group 15	VB	VA	nitrogen family	pentels, pnictogens*	pentels from Greek penta (five, V)
Group 16	VIB	VIA	oxygen family	chalcogens*
Group 17	VIIB	VIIA	fluorine family	halogens*
Group 18	Group 0	VIIIA	helium family or neon family	noble gases*

Some other names have been proposed and used without gaining wide acceptance: volatile metals for group 12; icosagens for group 13; crystallogens, adamantogens, and merylides for group 14; and aerogens for group 18.

CAS and old IUPAC numbering (A/B)

Two earlier group number systems exist: CAS (Chemical Abstracts Service) and old IUPAC. Both use numerals (Arabic or Roman) and letters A and B. Both systems agree on the numbers. The numbers indicate approximately the highest oxidation number of the elements in that group, and so indicate similar chemistry with other elements with the same numeral. The number proceeds in a linearly increasing fashion for the most part, once on the left of the table, and once on the right (see List of oxidation states of the elements), with some irregularities in the transition metals. However, the two systems use the letters differently. For example, potassium (K) has one valence electron. Therefore, it is located in group 1. Calcium (Ca) is in group 2, for it contains two valence electrons.

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 are designated to main group elements (A) and transition elements (B). The old IUPAC system was frequently used in Europe, while the CAS is 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 new system simply numbers the groups increasingly from left to right on the standard periodic table. The IUPAC proposal was first circulated in 1985 for public comments,^[2] and was later included as part of the 1990 edition of the Nomenclature of Inorganic Chemistry.^[5]

References

^ "The Periodic Table Terms". www.shmoop.com. Retrieved 2018-09-15..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"""""""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}

^ ^a^b Fluck, E. (1988). "New Notations in the Periodic Table" (PDF). Pure Appl. Chem. IUPAC. 60 (3): 431–436. doi:10.1351/pac198860030431. Retrieved 24 March 2012.

^ IUPAC (2005). "Nomenclature of inorganic chemistry" (PDF).

^ "The constitution of group 3 of the periodic table". IUPAC. 2015-12-18.

^ Leigh, G. J. Nomenclature of Inorganic Chemistry: Recommendations 1990. Blackwell Science, 1990.
ISBN 0-632-02494-1.

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Group (periodic table)

Contents

Group names

CAS and old IUPAC numbering (A/B)

See also

References

Further reading

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