Editing Period 5 element (section)

===Yttrium===
{{main|Yttrium}}
'''Yttrium''' is a [[chemical element]] with symbol '''Y''' and [[atomic number]] 39. It is a silvery-metallic [[transition metal]] chemically similar to the [[lanthanide]]s and it has often been classified as a "[[rare earth element]]".<ref name="IUPAC">{{cite book
 |author=IUPAC contributors
 |title=Nomenclature of Inorganic Chemistry: IUPAC Recommendations 2005
 |editor=N G Connelly |editor2=T Damhus |editor3=R M Hartshorn |editor4=A T Hutton
 |page=51
 |year=2005
 |isbn=0-85404-438-8
 |url=http://www.iupac.org/publications/books/rbook/Red_Book_2005.pdf
 |access-date=2007-12-17
 |publisher=RSC Publishing
 |url-status=dead
 |archive-url=https://web.archive.org/web/20090304204436/http://www.iupac.org/publications/books/rbook/Red_Book_2005.pdf
 |archive-date=2009-03-04
}}</ref> Yttrium is almost always found combined with the lanthanides in [[rare earth mineral]]s and is never found in nature as a free element. Its only stable [[isotope]], <sup>89</sup>Y, is also its only naturally occurring isotope.

In 1787, [[Carl Axel Arrhenius]] found a new mineral near [[Ytterby]] in Sweden and named it ''[[gadolinite|ytterbite]]'', after the village. [[Johan Gadolin]] discovered yttrium's oxide in Arrhenius' sample in 1789,<ref name="Krogt">[[Yttrium#Krogt|Van der Krogt 2005]]</ref> and [[Anders Gustaf Ekeberg]] named the new oxide ''[[yttria]]''. Elemental yttrium was first isolated in 1828 by [[Friedrich Wöhler]].<ref name="CRC2008">{{Cite book|author = CRC contributors|editor = Lide, David R.|chapter = Yttrium
|year = 2007–2008|title = CRC Handbook of Chemistry and Physics|volume = 4
|page = 41|location = New York|publisher = [[CRC Press]]|isbn = 978-0-8493-0488-0}}</ref>

The most important use of yttrium is in making [[phosphor]]s, such as the red ones used in television set [[cathode-ray tube]] (CRT) displays and in [[LED]]s.<ref name="Cotton">{{cite book|title=Encyclopedia of Inorganic Chemistry|first=Simon A. |last=Cotton| doi= 10.1002/0470862106.ia211 |date= 2006-03-15|chapter=Scandium, Yttrium & the Lanthanides: Inorganic & Coordination Chemistry|isbn=0-470-86078-2}}</ref> Other uses include the production of [[electrode]]s, [[electrolyte]]s, [[electronic filters]], [[laser]]s and [[superconductor]]s; various medical applications; and as [[Trace element|traces]] in various materials to enhance their properties. Yttrium has no known biological role, and exposure to yttrium compounds can cause lung disease in humans.<ref name="osha">{{cite web|author = OSHA contributors|url = http://www.osha.gov/SLTC/healthguidelines/yttriumandcompounds/recognition.html|title = Occupational Safety and Health Guideline for Yttrium and Compounds|access-date = 2008-08-03|publisher = United States Occupational Safety and Health Administration|date = 2007-01-11|url-status = dead|archive-url = https://web.archive.org/web/20130302060936/http://www.osha.gov/SLTC/healthguidelines/yttriumandcompounds/recognition.html|archive-date = 2013-03-02}} (public domain text)</ref>