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The lanthanide (/ˈlænθənaɪd/) or lanthanoid (/ˈlænθənɔɪd/) series of chemical elements[a] comprises at least the 14 metallic chemical elements with atomic numbers 57–70, from lanthanum through ytterbium. In the periodic table, they fill the 4f orbitals.[2][3][4] Lutetium (element 71) is also sometimes considered a lanthanide, despite being a d-block element and a transition metal.
The informal chemical symbol Ln is used in general discussions of lanthanide chemistry to refer to any lanthanide.[5] All but one of the lanthanides are f-block elements, corresponding to the filling of the 4f electron shell. Lutetium is a d-block element (thus also a transition metal),[6][7] and on this basis its inclusion has been questioned; however, like its congeners scandium and yttrium in group 3, it behaves similarly to the other 14. The term rare-earth element or rare-earth metal is often used to include the stable group 3 elements Sc, Y, and Lu in addition to the 4f elements.[8] All lanthanide elements form trivalent cations, Ln3+, whose chemistry is largely determined by the ionic radius, which decreases steadily from lanthanum (La) to lutetium (Lu).
These elements are called lanthanides because the elements in the series are chemically similar to lanthanum. Because "lanthanide" means "like lanthanum", it has been argued that lanthanum cannot logically be a lanthanide, but the International Union of Pure and Applied Chemistry (IUPAC) acknowledges its inclusion based on common usage.[1]
In presentations of the periodic table, the f-block elements are customarily shown as two additional rows below the main body of the table.[2] This convention is entirely a matter of aesthetics and formatting practicality; a rarely used wide-formatted periodic table inserts the 4f and 5f series in their proper places, as parts of the table's sixth and seventh rows (periods), respectively.
The 1985 IUPAC "Red Book" (p. 45) recommends using lanthanoid instead of lanthanide, as the ending -ide normally indicates a negative ion. However, owing to widespread current use, lanthanide is still allowed.
- ^ a b Cite error: The named reference
Greenwood&Earnshawwas invoked but never defined (see the help page). - ^ a b Gray, Theodore (2009). The Elements: A Visual Exploration of Every Known Atom in the Universe. New York: Black Dog & Leventhal Publishers. p. 240. ISBN 978-1-57912-814-2.
- ^ Lanthanide Archived 11 September 2011 at the Wayback Machine, Encyclopædia Britannica on-line
- ^ Holden, Norman E.; Coplen, Tyler (January–February 2004). "The Periodic Table of the Elements". Chemistry International. 26 (1): 8. doi:10.1515/ci.2004.26.1.8.
- ^ Liu, Qiong (2013). "Lanthanides and Cancer". Encyclopedia of Metalloproteins. pp. 1103–1110. doi:10.1007/978-1-4614-1533-6_153. ISBN 978-1-4614-1532-9.
- ^ 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 16 August 2021. Retrieved 28 January 2021.
- ^ Scerri, Eric (18 January 2021). "Provisional Report on Discussions on Group 3 of the Periodic Table". Chemistry International. 43 (1): 31–34. doi:10.1515/ci-2021-0115. S2CID 231694898.
- ^ F Block Elements, Oxidation States, Lanthanides and Actinides Archived 31 March 2021 at the Wayback Machine. Chemistry.tutorvista.com. Retrieved on 14 December 2017.
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