Group ( periodic table ) - wikipedia Group ( periodic table ) In the periodic table of the elements, each numbered column is a group. In chemistry, a group ( also known as a family ) 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 chalcogens. Contents 1 Group names 2 CAS and old IUPAC numbering ( A / B ) 3 References 4 Further reading Group names In history, several sets of group names have been used : hide Groups in the Periodic table IUPAC group 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Mendeleev ( I -- VIII ) IA II A III B IV B VB VI B VII B VIII B IB II B III B IV B VB VI B VII 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 VIII B IB IIB IIIB IVB VB VIB VIIB 0 Trivial name Alkali metals Alkaline earth metals Coinage metals Triels Tetrels Pnictogens Chalcogens Halogens Noble gases Name by element 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 He Period 2 Li Be Ne Period 3 Na Mg Al Si Cl Ar Period 4 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 Xe Period 6 Cs Ba La Ce -- Lu Hf Ta 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 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, Lu and Lr, or ( 2 ) Sc, Y, La and Ac. 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. Group name as recommended by IUPAC. Hydrogen ( H ), while placed in group 1, is not considered to be part of the alkali metals. New IUPAC names Old IUPAC ( 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, and was later included as part of the 1990 edition of the Nomenclature of Inorganic Chemistry. References ^ Jump up to : 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. Jump up ^ IUPAC ( 2005 ). `` Nomenclature of inorganic chemistry '' ( PDF ). Jump up ^ `` The constitution of group 3 of the periodic table ''. IUPAC. 2015 - 12 - 18. Jump up ^ 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. hide Periodic table Periodic table forms Standard 18 - column 18 - column, large cells 32 - column, large cells Alternative Alternatives Janet 's left step table Extended Extension beyond the 7th period Aufbau Fricke Pyykkö Sets of elements By periodic table structure Groups 1 ( Alkali metals ) 2 ( Alkaline earth metals ) 5 6 7 8 9 10 11 12 13 14 15 ( Pnictogens ) 16 ( Chalcogens ) 17 ( Halogens ) 18 ( Noble gases ) Periods 5 6 7 8 + Aufbau Fricke Pyykkö Blocks s - block p - block d - block f - block g - block Aufbau principle By metallicity Metals Alkali metals Alkaline earth metals Lanthanides Actinides Transition metals Post-transition metals Metalloids Lists of metalloids by source Dividing line Nonmetals Reactive nonmetals Noble gases Other sets Nutritional elements Platinum - group metals ( PGM ) Rare - earth elements Refractory metals Precious metals Coinage metals Noble metal Heavy metals Native metals Transuranium elements Transactinide elements Major actinides Minor actinides Elements Lists By : Abundance ( in humans ) Atomic properties Nuclear stability Production Symbol Properties Atomic weight Crystal structure Electron affinity Electron configuration Electronegativity Allen Pauling Goldschmidt classification Maximum valence Data pages Abundance Atomic radius Boiling point Critical point Density Elasticity Electrical resistivity Electron affinity Electron configuration Electronegativity Hardness Heat capacity Heat of fusion Heat of vaporization Ionization energy Melting point Oxidation state Speed of sound Thermal conductivity Thermal expansion coefficient Vapor pressure History Element discoveries Mendeleev 's predictions Naming etymology controversies for places for people in East Asia See also IUPAC nomenclature systematic element name Trivial name Dmitri Mendeleev Book Chemistry Portal Retrieved from `` https://en.wikipedia.org/w/index.php?title=Group_(periodic_table)&oldid=841432685 '' Categories : Periodic table Groups ( periodic table ) Hidden categories : All articles with unsourced statements Articles with unsourced statements from March 2018 Talk Contents About Wikipedia Afrikaans Alemannisch Aragonés Asturianu Azərbaycanca Bân - lâm - gú Беларуская Български Bosanski Brezhoneg Català Čeština Cymraeg Dansk Deutsch Ελληνικά Esperanto Euskara فارسی Français Frysk Gaeilge Galego 한국어 हिन्दी Hrvatski Bahasa Indonesia Interlingua Íslenska Italiano Basa Jawa Latina Latviešu Lumbaart Македонски Māori Bahasa Melayu Монгол Nederlands 日本 語 Norsk Norsk nynorsk ଓଡ଼ିଆ ភាសា ខ្មែរ Plattdüütsch Polski Português Română Русский Shqip Simple English Slovenčina Slovenščina Српски / srpski Srpskohrvatski / српскохрватски Basa Sunda Suomi Svenska தமிழ் ไทย Türkçe Українська اردو Tiếng Việt West - Vlams 中文 58 more Edit links This page was last edited on 15 May 2018, at 20 : 25 ( UTC ). 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Question: what is the same within each group on the periodic table
Answer: core charge