Editing Magnesium (section)

== Characteristics ==
=== Physical properties ===
Elemental magnesium is a gray-white lightweight metal, two-thirds the density of aluminium. Magnesium has the lowest melting ({{convert|923|K|°C}}) and the lowest boiling point ({{convert|1363|K|°C}}) of all the alkaline earth metals.<ref>{{Cite web |title=alkaline-earth metal – Physical and chemical behaviour |url=https://www.britannica.com/science/alkaline-earth-metal/Physical-and-chemical-behaviour |access-date=2022-03-27 |website=Encyclopædia Britannica |language=en}}</ref>

Pure polycrystalline magnesium is brittle and easily fractures along [[shear band]]s. It becomes much more [[ductility|malleable]] when alloyed with small amounts of other metals, such as 1% aluminium.<ref>{{cite journal |doi=10.1038/s41598-017-10384-0 |pmid=28874798 |pmc=5585333 |title=A rare-earth free magnesium alloy with improved intrinsic ductility |journal=Scientific Reports |volume=7 |issue=1 |pages=10458 |year=2017 |last1=Sandlöbes |first1=S. |last2=Friák |first2=M. |last3=Korte-Kerzel |first3=S. |last4=Pei |first4=Z. |last5=Neugebauer |first5=J. |last6=Raabe |first6=D. |bibcode=2017NatSR...710458S}}</ref> The malleability of polycrystalline magnesium can also be significantly improved by reducing its grain size to about 1&nbsp;[[micrometre|μm]] or less.<ref>{{cite journal |doi=10.1038/s41467-017-01330-9 |pmid=29042555 |pmc=5715137 |title=Super-formable pure magnesium at room temperature |journal=Nature Communications |volume=8 |issue=1 |pages=972 |year=2017 |last1=Zeng |first1=Zhuoran |last2=Nie |first2=Jian-Feng |last3=Xu |first3=Shi-Wei |last4=Davies |first4=Chris H. J. |last5=Birbilis |first5=Nick |bibcode=2017NatCo...8..972Z}}</ref>

When finely powdered, magnesium reacts with water to produce hydrogen gas:
: Mg(s) + 2 H<sub>2</sub>O(g) → Mg(OH)<sub>2</sub>(aq) + H<sub>2</sub>(g) + 1203.6&nbsp;kJ/mol
However, this reaction is much less dramatic than the reactions of the alkali metals with water, because the magnesium hydroxide builds up on the surface of the magnesium metal and inhibits further reaction.<ref>{{Cite web |date=2013-10-03 |title=Reactions of Group 2 Elements with Water |url=https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Supplemental_Modules_and_Websites_(Inorganic_Chemistry)/Descriptive_Chemistry/Elements_Organized_by_Block/1_s-Block_Elements/Group__2_Elements%3A_The_Alkaline_Earth_Metals/1Group_2%3A_Chemical_Reactions_of_Alkali_Earth_Metals/Reactions_of_Group_2_Elements_with_Water |access-date=2022-03-27 |website=Chemistry LibreTexts |language=en}}</ref>

=== Chemical properties ===
====Oxidation====
The principal property of magnesium metal is its reducing power. One hint is that it [[tarnish]]es slightly when exposed to air, although, unlike the heavier [[alkaline earth metals]], an oxygen-free environment is unnecessary for storage because magnesium is protected by a thin layer of oxide that is fairly impermeable and difficult to remove.<ref name=":0">{{Cite web |last=MMTA |title=Magnesium |url=https://mmta.co.uk/metals/mg/ |access-date=2023-11-08 |website=MMTA |language=en-US}}</ref>

Direct reaction of magnesium with air or oxygen at ambient pressure forms only the "normal" oxide MgO. However, this oxide may be combined with hydrogen peroxide to form [[magnesium peroxide]], MgO<sub>2</sub>, and at low temperature the peroxide may be further reacted with ozone to form magnesium superoxide Mg(O<sub>2</sub>)<sub>2</sub>.<ref>{{cite journal |last1=Vol'nov |first1=I. I. |last2=Tokareva |first2=S. A. |last3=Belevskii |first3=V. N. |last4=Latysheva |first4=E. I. |title=The formation of magnesium perperoxide Mg(O2)2 in the reaction of magnesium peroxide with ozone |journal=Bulletin of the Academy of Sciences of the USSR Division of Chemical Science |date=March 1970 |volume=19 |issue=3 |pages=468–471 |doi=10.1007/bf00848959 }}</ref>

Magnesium reacts with nitrogen in the solid state if it is powdered and heated to just below the melting point, forming [[Magnesium nitride]] Mg<sub>3</sub>N<sub>2</sub>.<ref>{{Cite journal|last1=Zong|first1=Fujian|last2=Meng|first2=Chunzhan|last3=Guo|first3=Zhiming|last4=Ji|first4=Feng|last5=Xiao|first5=Hongdi|last6=Zhang|first6=Xijian|last7=Ma|first7=Jin|last8=Ma|first8=Honglei|title=Synthesis and characterization of magnesium nitride powder formed by Mg direct reaction with N2|journal=_Journal of Alloys and Compounds|year=2010 |volume=508|issue=1|pages=172–176|doi=10.1016/j.jallcom.2010.07.224}}</ref>

Magnesium reacts with water at room temperature, though it reacts much more slowly than calcium, a similar group 2 metal.<ref name=":0" /> When submerged in water, [[hydrogen]] bubbles form slowly on the surface of the metal; this reaction happens much more rapidly with powdered magnesium.<ref name=":0" /> The reaction also occurs faster with higher temperatures (see {{slink|#Safety precautions}}). Magnesium's reversible reaction with water can be harnessed to store energy and run a [[Magnesium injection cycle|magnesium-based engine]]. Magnesium also reacts exothermically with most acids such as [[hydrochloric acid]] (HCl), producing [[magnesium chloride]] and hydrogen gas, similar to the HCl reaction with aluminium, zinc, and many other metals.<ref>{{Cite web |title=The rate of reaction of magnesium with hydrochloric acid |url=https://edu.rsc.org/experiments/the-rate-of-reaction-of-magnesium-with-hydrochloric-acid/1916.article |access-date=2023-11-08 |website=RSC Education |language=en}}</ref> Although it is difficult to ignite in mass or bulk, magnesium metal will ignite.

Magnesium may also be used as an igniter for [[thermite]], a mixture of aluminium and iron oxide powder that ignites only at a very high temperature.

====Organic chemistry====
{{Further|Grignard reagent}}
Organomagnesium compounds are widespread in [[organic chemistry]]. They are commonly found as [[Grignard reagents]], formed by reaction of magnesium with [[haloalkane]]s. Examples of [[Grignard reagents]] are [[phenylmagnesium bromide]] and [[ethylmagnesium bromide]]. The [[Grignard reagents]] function as a common [[nucleophile]], attacking the [[electrophilic]] group such as the carbon atom that is present within the polar bond of a [[carbonyl]] group.

A prominent organomagnesium reagent beyond Grignard reagents is [[magnesium anthracene]], which is used as a source of highly active magnesium. The related [[butadiene]]-magnesium adduct serves as a source for the butadiene dianion.

Complexes of dimagnesium(I) have been observed.<ref>{{cite journal |last1=Rösch |first1=B. |last2=Gentner |first2=T. X. |last3=Eyselein |first3=J. |last4=Langer |first4=J. |last5=Elsen |first5=H. |last6=Harder |first6=S. |title=Strongly reducing magnesium(0) complexes |journal=Nature |date=29 April 2021 |volume=592 |issue=7856 |pages=717–721 |doi=10.1038/s41586-021-03401-w |pmid=33911274 |bibcode=2021Natur.592..717R |s2cid=233447380 }}</ref>

==== Detection in solution ====

The presence of magnesium ions can be detected by the addition of [[ammonium chloride]], [[ammonium hydroxide]] and [[monosodium phosphate]] to an aqueous or dilute HCl solution of the salt. The formation of a white precipitate indicates the presence of magnesium ions.

[[Azo violet]] dye can also be used, turning deep blue in the presence of an alkaline solution of magnesium salt. The color is due to the [[adsorption]] of azo violet by [[magnesium hydroxide|Mg(OH)<sub>2</sub>]].