Kullanıcı:Nanahuatl/Çalışma2: Revizyonlar arasındaki fark

The abundances of the noble gases in the universe decrease as their [[atomic number]]s increase. Helium is the most common element in the [[universe]] after hydrogen, with a mass fraction of about 24%. Most of the helium in the universe was formed during [[Big Bang nucleosynthesis]], but the amount of helium is steadily increasing due to the fusion of hydrogen in [[stellar nucleosynthesis]] (and, to a very slight degree, the [[alpha decay]] of heavy elements).<ref>{{cite web|last=Weiss|first=Achim|title=Elements of the past: Big Bang Nucleosynthesis and observation|url=http://www.einstein-online.info/en/spotlights/BBN_obs/index.html|publisher=[[Max Planck Institute for Gravitational Physics]]|accessdate=2008-06-23}}</ref><ref>{{cite journal|author=Coc, A.|title=Updated Big Bang Nucleosynthesis confronted to WMAP observations and to the Abundance of Light Elements|journal=[[Astrophysical Journal]]|volume=600|year=2004|pages=544–552|doi=10.1086/380121|bibcode=2004ApJ...600..544C|issue=2|arxiv= astro-ph/0309480 |display-authors=etal}}</ref> Abundances on Earth follow different trends; for example, helium is only the third most abundant noble gas in the atmosphere. The reason is that there is no [[primordial element|primordial]] helium in the atmosphere; due to the small mass of the atom, helium cannot be retained by the Earth's [[gravitational field]].<ref name=morrison>{{cite journal|first1=P.|last1=Morrison|last2=Pine|first2=J.|year=1955|title=Radiogenic Origin of the Helium Isotopes in Rock|journal=Annals of the New York Academy of Sciences|volume=62|issue=3|pages=71–92|doi=10.1111/j.1749-6632.1955.tb35366.x|bibcode= 1955NYASA..62...71M }}</ref> Helium on Earth comes from the [[alpha decay]] of heavy elements such as [[uranium]] and [[thorium]] found in the Earth's [[Crust (geology)|crust]], and tends to accumulate in [[Natural gas field|natural gas deposit]]s.<ref name=morrison /> The abundance of argon, on the other hand, is increased as a result of the [[beta decay]] of [[potassium-40]], also found in the Earth's crust, to form [[argon-40]], which is the most abundant isotope of argon on Earth despite being relatively rare in the [[Solar System]]. This process is the basis for the [[potassium-argon dating]] method.<ref>{{cite web|url=http://www.geoberg.de/text/geology/07011601.php|title=⁴⁰Ar/³⁹Ar dating and errors|accessdate=2008-06-26|publisher=[[Technische Universität Bergakademie Freiberg]]|date=2007-01-16|last=Scherer|first=Alexandra |archiveurl= https://web.archive.org/web/20071014042248/http://geoberg.de/text/geology/07011601.php |archivedate=2007-10-14}}</ref> Xenon has an unexpectedly low abundance in the atmosphere, in what has been called the ''missing xenon problem''; one theory is that the missing xenon may be trapped in minerals inside the Earth's crust.<ref>{{cite journal |first1=Chrystèle|last1=Sanloup |first2=Burkhard C. |last2=Schmidt |first3=Eva Maria Chamorro|last3=Perez |first4=Albert |last4=Jambon |first5=Eugene |last5=Gregoryanz |first6=Mohamed |last6=Mezouar |displayauthors=2 |title=Retention of Xenon in Quartz and Earth's Missing Xenon|journal=Science|year=2005|volume=310|issue=5751|pages=1174–1177|doi= 10.1126/science.1119070|pmid=16293758|bibcode= 2005Sci...310.1174S }}</ref> After the discovery of [[xenon dioxide]], research showed that Xe can substitute for Si in [[quartz]].<ref>{{cite web |title= Xenon Dioxide May Solve One of Earth's Mysteries |url= http://www.accn.ca/index.php?ci_id=2583&la_id=1 |author= Tyler Irving |publisher= L’Actualité chimique canadienne (Canadian Chemical News) |date= May 2011 |accessdate=2012-05-18}}</ref> Radon is formed in the [[lithosphere]] by the [[alpha decay]] of radium. It can seep into buildings through cracks in their foundation and accumulate in areas that are not well ventilated. Due to its high radioactivity, radon presents a significant health hazard; it is implicated in an estimated 21,000 [[lung cancer]] deaths per year in the United States alone.<ref>{{cite web| title= A Citizen's Guide to Radon| publisher= U.S. Environmental Protection Agency| date= 2007-11-26| url= http://www.epa.gov/radon/pubs/citguide.html| accessdate= 2008-06-26}}</ref>▼