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In [[chemistry]], a '''group''' (also known as a '''family'''<ref>{{Cite web|url=https://www.shmoop.com/periodic-table/terms.html|title=The Periodic Table Terms|website=www.shmoop.com|language=en|access-date=2018-09-15}}</ref>) is a column of elements in the [[periodic table]] of the [[chemical element]]s. 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 shell]]s of their atoms (i.e., the same [[core charge]]), as most chemical properties are dominated by the orbital location of the outermost electron. |
In [[chemistry]], a '''group''' (also known as a '''family'''<ref>{{Cite web|url=https://www.shmoop.com/periodic-table/terms.html|title=The Periodic Table Terms|website=www.shmoop.com|language=en|access-date=2018-09-15}}</ref>) is a column of elements in the [[periodic table]] of the [[chemical element]]s. 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 shell]]s of their atoms (i.e., the same [[core charge]]), as most chemical properties are dominated by the orbital location of the outermost electron. |
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There are three systems of group numbering for the groups, that often assign the same number to different groups. The modern numbering "group 1" to "group 18" has been recommended by the [[International Union of Pure and Applied Chemistry]] (IUPAC) since about 1990. It replaces two older incompatible naming schemes, used by the [[Chemical Abstract Service]] (CAS, more popular in the U. S.), and by IUPAC before 1990 (more popular in Europe). The system of eighteen groups is generally accepted by the chemistry community, but some dissent exists about membership of several elements. [[Period 1 element #Position of period 1 elements in the periodic table| |
There are three systems of group numbering for the groups, that often assign the same number to different groups. The modern numbering "group 1" to "group 18" has been recommended by the [[International Union of Pure and Applied Chemistry]] (IUPAC) since about 1990. It replaces two older incompatible naming schemes, used by the [[Chemical Abstract Service]] (CAS, more popular in the U. S.), and by IUPAC before 1990 (more popular in Europe). The system of eighteen groups is generally accepted by the chemistry community, but some dissent exists about membership of several elements. Disagreements mostly [[Period 1 element #Position of period 1 elements in the periodic table|involve elements number 1 and 2]] ([[hydrogen]] and [[helium]]), as well as [[inner transition metal]]s. |
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Groups may also 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 "[[chalcogen]]s". However, [[iron group]] usually does not mean "group 8". In chemistry it may mean either [[iron]], [[cobalt]], and [[nickel]], or some other set of elements with similar chemical properties. In [[astrophysics]] and [[nuclear physics]], it usually means those three plus [[chromium]] and [[manganese]]. |
Groups may also 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 "[[chalcogen]]s". However, [[iron group]] usually does not mean "group 8". In chemistry it may mean either [[iron]], [[cobalt]], and [[nickel]], or some other set of elements with similar chemical properties. In [[astrophysics]] and [[nuclear physics]], it usually means those three plus [[chromium]] and [[manganese]]. |
Revision as of 09:58, 15 August 2019
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 for the groups, that often assign the same number to different groups. The modern numbering "group 1" to "group 18" has been recommended by the International Union of Pure and Applied Chemistry (IUPAC) since about 1990. It replaces two older incompatible naming schemes, used by the Chemical Abstract Service (CAS, more popular in the U. S.), and by IUPAC before 1990 (more popular in Europe). The system of eighteen groups is generally accepted by the chemistry community, but some dissent exists about membership of several elements. Disagreements mostly involve elements number 1 and 2 (hydrogen and helium), as well as inner transition metals.
Groups may also 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". However, iron group usually does not mean "group 8". In chemistry it may mean either iron, cobalt, and nickel, or some other set of elements with similar chemical properties. In astrophysics and nuclear physics, it usually means those three plus chromium and manganese.
Group names
In history, several sets of group names have been used:[2][3]
IUPAC group | 1a | 2 | —b | 3c | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Mendeleev (I–VIII) | I | II | III | IV | V | VI | VII | VIII | I | II | III | IV | V | VI | VII | d | |||
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 | VIII | IB | IIB | IIIB | IVB | VB | VIB | VIIB | 0 | |||
Trivial namer | H and alkali metals | alkaline earth metals | triels | tetrels | pnictogens | chalcogens | halogens | noble gases | |||||||||||
Name by elementr | 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 | 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–Yb | Lu | Hf | Ta | W | Re | Os | Ir | Pt | Au | Hg | Tl | Pb | Bi | Po | At | Rn |
Period 7 | Fr | Ra | Ac–No | Lr | Rf | Db | Sg | Bh | Hs | Mt | Ds | Rg | Cn | Nh | Fl | Mc | Lv | Ts | Og |
b The 14 f-block groups (columns) do not have a group number.
c The correct composition of group 3 is scandium (Sc), yttrium (Y), lutetium (Lu), and lawrencium (Lr), as shown here: this is endorsed by 1988[4] and 2021[5] IUPAC reports on the question. General inorganic chemistry texts often put scandium (Sc), yttrium (Y), lanthanum (La), and actinium (Ac) in group 3, so that Ce–Lu and Th–Lr become the f-block between groups 3 and 4; this was based on incorrectly measured electron configurations from history,[6] and Lev Landau and Evgeny Lifshitz already considered it incorrect in 1948.[7] Arguments can still occasionally be encountered in the contemporary literature purporting to defend it, but most authors consider them logically inconsistent.[8][9][10] Some sources follow a compromise that puts La–Lu and Ac–Lr as the f-block rows (despite that giving 15 f-block elements in each row, which contradicts quantum mechanics), leaving the heavier members of group 3 ambiguous.[5] See also Group 3 element#Composition.
d 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.
Group 1 (previously group IA)[11] according to IUPAC is composed of hydrogen (H) and the alkali metals. Elements of the group have one s-electron (s1) in the outer electron shell. Hydrogen has no analogs and is not considered to be an alkali metal as it rarely exhibits behaviour comparable to that of the alkali metals. This makes the group somewhat exceptional.
New IUPAC name |
Old IUPAC (Europe) |
CAS name (U.S.) |
Name by element |
IUPAC recommended trivial name |
Other trivial name |
---|---|---|---|---|---|
Group 1 | IA | IA | lithium family |
hydrogen and alkali metals* |
|
Group 2 | IIA | IIA | beryllium family | alkaline earth metals* | |
Group 3 | IIIA | IIIB | scandium family | ||
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 from Greek tri (three, III) | |
Group 14 | IVB | IVA | carbon family | tetrels from Greek tetra (four, IV) | |
Group 15 | VB | VA | nitrogen family | pnictogens* | pentels from Greek penta (five, V) |
Group 16 | VIB | VIA | oxygen family | chalcogens* | |
Group 17 | VIIB | VIIA | fluorine family | halogens* | |
Group 18 | 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.[citation needed]
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.[12]
See also
References
- ^ "The Periodic Table Terms". www.shmoop.com. Retrieved 2018-09-15.
- ^ a b Fluck, E. (1988). "New Notations in the Periodic Table" (PDF). Pure Appl. Chem. 60 (3). IUPAC: 431–436. doi:10.1351/pac198860030431. Retrieved 24 March 2012.
- ^ IUPAC (2005). "Nomenclature of inorganic chemistry" (PDF).
- ^ Fluck, E. (1988). "New Notations in the Periodic Table" (PDF). Pure Appl. Chem. 60 (3): 431–436. doi:10.1351/pac198860030431. S2CID 96704008. Archived (PDF) from the original on 25 March 2012. Retrieved 24 March 2012.
- ^ a b Scerri, Eric (18 January 2021). "Provisional Report on Discussions on Group 3 of the Periodic Table" (PDF). Chemistry International. 43 (1): 31–34. doi:10.1515/ci-2021-0115. S2CID 231694898. Archived (PDF) from the original on 13 April 2021. Retrieved 9 April 2021.
- ^ William B. Jensen (1982). "The Positions of Lanthanum (Actinium) and Lutetium (Lawrencium) in the Periodic Table". J. Chem. Educ. 59 (8): 634–636. Bibcode:1982JChEd..59..634J. doi:10.1021/ed059p634.
- ^ L. D. Landau, E. M. Lifshitz (1958). Quantum Mechanics: Non-Relativistic Theory. Vol. 3 (1st ed.). Pergamon Press. pp. 256–7.
- ^ Jensen, William B. (2015). "The positions of lanthanum (actinium) and lutetium (lawrencium) in the periodic table: an update". Foundations of Chemistry. 17: 23–31. doi:10.1007/s10698-015-9216-1. S2CID 98624395. Archived from the original on 30 January 2021. Retrieved 28 January 2021.
- ^ Scerri, Eric (2009). "Which Elements Belong in Group 3?". Journal of Chemical Education. 86 (10): 1188. doi:10.1021/ed086p1188. Retrieved 1 January 2023.
- ^ Chemey, Alexander T.; Albrecht-Schmitt, Thomas E. (2019). "Evolution of the periodic table through the synthesis of new elements". Radiochimica Acta. 107 (9–11): 1–31. doi:10.1515/ract-2018-3082.
- ^ Fluck, E. (1988). "New Notations in the Periodic Table" (PDF). Pure Appl. Chem. 60 (3). IUPAC: 431–436. doi:10.1351/pac198860030431. Retrieved 24 March 2012.
- ^ Leigh, G. J. Nomenclature of Inorganic Chemistry: Recommendations 1990. Blackwell Science, 1990. ISBN 0-632-02494-1.
Further reading
- Scerri, E. R. (2007). The periodic table, its story and its significance. Oxford University Press. ISBN 978-0-19-530573-9.