Editing Period 3 element (section)

=== Magnesium ===
{{Main|Magnesium}}
''Magnesium'' (symbol '''Mg''') is an [[alkaline earth metal]] and has common oxidation number +2. It is the eighth most [[abundance of the chemical elements|abundant element]] in the [[Earth's crust]]<ref name="Abundance">{{cite web |first=L. Bruce |last=Railsback |title=Abundance and form of the most abundant elements in Earth's continental crust |access-date=2008-02-15 |url=http://railsback.org/Fundamentals/ElementalAbundanceTableP.pdf |website=Some Fundamentals of Mineralogy and Geochemistry |archive-date=2011-09-27 |archive-url=https://web.archive.org/web/20110927064201/http://www.gly.uga.edu/railsback/Fundamentals/ElementalAbundanceTableP.pdf |url-status=live }}</ref> and the ninth in the known [[universe]] as a whole.<ref>{{Housecroft3rd|pages=305–306}}</ref><ref>{{cite book|last=Ash|first=Russell|title=The Top 10 of Everything 2006: The Ultimate Book of Lists|publisher=Dk Pub|year=2005|url=http://plymouthlibrary.org/faqelements.htm|isbn=0-7566-1321-3|url-status=dead|archive-url=https://web.archive.org/web/20100210170504/http://plymouthlibrary.org/faqelements.htm|archive-date=2010-02-10}}</ref> Magnesium is the fourth most common element in the Earth as a whole (behind iron, oxygen and silicon), making up 13% of the planet's mass and a large fraction of the planet's [[mantle (geology)|mantle]]. It is relatively abundant because it is easily built up in [[supernova]] stars by sequential additions of three helium nuclei to carbon (which in turn is made from three helium nuclei). Due to the magnesium ion's high [[solubility]] in water, it is the third most abundant element dissolved in [[seawater]].<ref>{{cite news|url=http://www.seafriends.org.nz/oceano/seawater.htm#composition|title=The chemical composition of seawater|author=Anthoni, J Floor|year=2006}}</ref>

The free element (metal) is not found naturally on Earth, as it is highly reactive (though once produced, it is coated in a thin layer of oxide [see [[Passivation (chemistry)|passivation]]], which partly masks this reactivity). The free metal burns with a characteristic brilliant white light, making it a useful ingredient in flares. The metal is now mainly obtained by [[electrolysis]] of magnesium salts obtained from [[brine]]. Commercially, the chief use for the metal is as an [[alloy]]ing agent to make [[aluminium]]-magnesium alloys, sometimes called "[[magnalium]]" or "magnelium". Since magnesium is less dense than aluminium, these alloys are prized for their relative lightness and strength.

Magnesium ions are sour to the taste, and in low concentrations help to impart a natural tartness to fresh [[mineral water]]s.