Revision 468758944 of "User:Double sharp/Alkaline earth metal" on enwiki

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{| style="float: right; border: 1px solid #ccc; margin: 0.5em 0pt 0.8em 1.4em; padding: 3px !important; width: 150px;"
! [[Group (periodic table)|Group]]
!
! 2
|-
! [[Period (periodic table)|Period]] 
! [[Period 2 element|2]]
| {{element cell|[[File:Be-140g.jpg|150px|Lump of beryllium]]<br> 4|Beryllium|Be| |Solid|Alkaline earth metals|Primordial}}
|-
!
! [[Period 3 element|3]]
| {{element cell|[[File:Magnesium crystals.jpg|150px|Magnesium crystals]]<br>12|Magnesium|Mg| |Solid|Alkaline earth metals|Primordial}}
|-
!
! [[Period 4 element|4]]
| {{element cell|[[File:Calcium unter Argon Schutzgasatmosphäre.jpg|150px|Calcium stored under argon atmosphere]]<br>20|Calcium|Ca| |Solid|Alkaline earth metals|Primordial}}
|-
!
! [[Period 5 element|5]]
| {{element cell|[[File:Strontium destilled crystals.jpg|150px|Strontium floating in paraffin oil]]<br>38|Strontium|Sr| |Solid|Alkaline earth metals|Primordial}}
|-
!
! [[Period 6 element|6]]
| {{element cell|[[File:Barium unter Argon Schutzgas Atmosphäre.jpg|150px|Barium stored under argon atmosphere]]<br>56|Barium|Ba| |Solid|Alkaline earth metals|Primordial}}
|-
!
! [[Period 7 element|7]]
| {{element cell|[[File:Radium226.jpg|150px|Radium electroplated on copper foil and covered with polyurethane to prevent reaction with air]]<br>88|Radium|Ra| |Solid|Alkaline earth metals|Natural radio}}
|}

The '''alkaline earth metals''' are a [[group (periodic table)|group]] in the [[periodic table]]. In the modern [[IUPAC]] nomenclature, the alkaline earth metals are called the '''group 2 elements'''. Previously, they were called the '''Group IIA elements''' (pronounced "group two A", as the "II" here is a [[Roman numeral]]). The alkaline earth metals contain '''[[beryllium]] (Be)''', '''[[magnesium]] (Mg)''', '''[[calcium]] (Ca)''', '''[[strontium]] (Sr)''', '''[[barium]] (Ba)''' and '''[[radium]] (Ra)'''.<ref>{{cite book |url= http://old.iupac.org/publications/books/rbook/Red_Book_2005.pdf |title= Nomenclature of Inorganic Chemistry. IUPAC Recommendations 2005 |page= 51 |publisher= [[International Union of Pure and Applied Chemistry]] |year= 2005 }}</ref> (Although '''[[helium]] (He)''' is occasionally considered to be a group 2 element, for example, in the [[extended periodic table]] and [[Charles Janet#Chemical ideas|Janet periodic table]], it never exhibits behaviour comparable to the alkaline earth metals.) The group lies in the [[s-block]] of the periodic table.

This specific group in the periodic table owes its name to their oxides that simply give basic alkaline solutions. These oxides melt at such high temperature that they remain solids ("earths") in fires. The alkaline earth metals provide a good example of group trends in properties in the periodic table, with well-characterized [[homology (chemistry)|homologous]] behavior down the group. With the exception of [[beryllium]] and [[magnesium]], the metals have a distinguishable flame color, orange for [[calcium]], bright red for [[strontium]], green for [[barium]] and crimson red for [[radium]].

All of the alkaline earth metals discovered, as of 2011, are naturally occurring (see [[abundance of the chemical elements]] for references), and share similar properties: they are all rather [[reactivity (chemistry)|reactive]] metals under standard conditions. So far, experiments have been conducted to attempt the synthesis of the next member of the group, '''[[unbinilium]] (Ubn)''', but these have all met with failure. However, since unbinilium is the second [[period 8 element]] and only the second element on the periodic table that has not been discovered yet, it is likely to be discovered in the near future. It is also possible that '''[[ununhexium]] (Uuh)''', which has been synthesised in [[2002]], is the next alkaline earth metal.

Like other groups, the members of this family show patterns in its electron configuration, especially the outermost shells resulting in trends in chemical behavior:

{| class="wikitable" border="1" cellpadding="3" cellspacing="0"
|-
![[Atomic number|Z]] !! [[Chemical element|Element]] !! [[Electron shell|No. of electrons/shell]]
|-
| 4 || Beryllium || 2, 2
|-
| 12 || Magnesium || 2, 8, 2
|-
| 20 || Calcium || 2, 8, 8, 2
|-
| 38 || Strontium || 2, 8, 18, 8, 2
|-
| 56 || Barium || 2, 8, 18, 18, 8, 2
|-
| 88 || Radium || 2, 8, 18, 32, 18, 8, 2
|}

The alkaline earth metals are silver colored, soft [[metal]]s, which react readily with [[halogen]]s to form [[ionic salt]]s, and with [[water]], though not as rapidly as the [[alkali metal]]s, to form strong [[alkali]]ne ([[base (chemistry)|basic]]) [[hydroxide]]s. For example, where [[lithium]], [[sodium]] and [[potassium]] react with water at room temperature, [[magnesium]] reacts only with [[steam]] and [[calcium]] with hot water:

:Mg + 2 H<sub>2</sub>O → Mg(OH)<sub>2</sub> + H<sub>2</sub>

[[Beryllium]] is an exception: It does not react with water or steam, and its halides are covalent.

All the alkaline earth metals have two [[electron]]s in their valence shell, so the energetically preferred state of achieving a filled [[electron shell]] is to lose two electrons to form doubly [[electric charge|charged]] [[Positive (electricity)|positive]] [[ion]]s.

The alkaline earth metals are named after their [[oxide]]s, the ''alkaline earths'', whose old-fashioned names were [[beryllia]], [[Magnesium oxide|magnesia]], [[Calcium oxide|lime]], [[strontia]] and [[baryta]].  These oxides are basic (alkaline) when combined with water. "Earth" is an old term applied by early chemists to nonmetallic substances that are insoluble in water and resistant to heating—properties shared by these oxides. The realization that these earths were not elements but [[chemical compound|compound]]s is attributed to the chemist [[Antoine Lavoisier]].  In his ''[[Traité Élémentaire de Chimie]]'' (''Elements of Chemistry'') of 1789 he called them salt-forming earth elements. Later, he suggested that the alkaline earths might be metal oxides, but admitted that this was mere conjecture.  In 1808, acting on Lavoisier's idea, [[Humphry Davy]] became the first to obtain samples of the metals by [[electrolysis]] of their molten earths.

==Biological occurrences==
[[Image:Erdalkali.jpg|thumb|300px|right|The first five alkaline earth metals.]]

* Beryllium's low aqueous solubility means it is rarely available to biological systems; it has no known role in living organisms, and when encountered by them, is usually highly toxic.

* Magnesium and calcium are ubiquitous and essential to all known living organisms. They are involved in more than one role, with, for example, Mg/Ca [[ion pumps]] playing a role in some cellular processes, magnesium functioning as the active center in some [[enzymes]], and calcium salts taking a structural role (e.g. [[bone]]s).

* Strontium and barium have a lower availability in the biosphere. Strontium plays an important role in marine aquatic life, especially hard corals.  They use strontium to build their [[exoskeleton]]. These elements have some uses in medicine, for example "[[barium meal]]s" in radiographic imaging, whilst strontium compounds are employed in some [[toothpaste]]s.

* Radium has a low availability and is highly radioactive, making it toxic to life.
<br clear="all" />

== Comparison of the physical properties and chemical properties between alkaline earth and alkali metals ==

Just like their names, they do not differ completely. The main difference is the electron configuration, which is ns<sup>2</sup> for alkaline earth metals and ns<sup>1</sup> for alkali metals. For the alkaline earth metals, there are two electrons that are available to form a metallic bond, and the nucleus contains an additional positive charge. Also, the elements of group 2A (alkaline earth) have much higher melting points and boiling points compared to those of group 1A (alkali metals). The alkali also have a softer and more lighweight figure whereas the alkaline earth metals are much harder and denser.
	
The second valence electron is very important when it comes to comparing chemical properties of the alkaline earth and the alkali metals. The second valence electron is in the same “sublevel” as the first valence electron. Therefore, the Z<sub>eff</sub> is much greater.  This means that the elements of the group 2A contain a smaller atomic radius and much higher ionization energy than the group 1A. Even though the group 2A contains much higher ionization energy, they still form an ionic compound with 2+ cations. Beryllium, however, behaves differently. This is because in order to remove two electrons from this particular atom, it requires significantly more energy. It never forms Be<sup>2+</sup> and its bonds are polar covalent.

== Beryllium ==
As mentioned earlier, Be is “special”; it behaves differently. If the Be<sup>2+</sup> ion did exist, it would polarize electron clouds that are near it very strongly and would cause extensive [[orbital overlap]], since Be has a high charge density. All compounds that include Be have a covalent bond. Even the compound BeF<sub>2</sub> , which is the most ionic Be compound, has a low melting point and a low electrical conductivity when melted.

== Important reactions and compounds ==
'''Reactions''':<br />
Note: E = elements that act as reducing agents<br />
1.	The metals reduce halogens to form ionic halides: E<sub>(s)</sub> + X<sub>2</sub> → EX<sub>2</sub> <sub>(s)</sub>  where X = F, Cl, Br or I<br />
2.	The metals reduce O<sub>2</sub> to form the oxides: 2E<sub>(s)</sub> + O<sub>2</sub> → 2EO<sub>(s)</sub><br />
3.	The larger metals react with water to produce hydrogen gas: E<sub>(s)</sub> + 2H<sub>2</sub>O<sub>(l)</sub> → E<sup>2+</sup><sub>(aq)</sub> + 2OH<sup>-</sup><sub>aq</sub> + H<sub>2</sub> <sub>(g)</sub> where E = Ca, Sr or Ba<br />
<br />
'''Compounds'''<br />
1.	Alkylmagnesium halides (RMgX where R = hydrocarbon group and X = halogen). They are used to synthetise organic compounds. <br />Here’s an example: 3RMgCl + SnCl<sub>4</sub> → 3MgCl<sub>2</sub> + R<sub>3</sub>SnCl<br />
2.	Magnesium oxide (MgO). It is used as a material to refract furnace brick and wire insulation (melting point of 2852°C).<br />
3.	Calcium carbonate (CaCO<sub>3</sub>). It is mainly used in the construction industry and for making limestone, marble, chalk, and coral.

==References==
<references/>
*[http://www.chemsoc.org/visElements/pages/data/intro_groupii_data.html Group 2 - Alkaline Earth Metals], Royal Chemistry Society.
*[http://www.wpbschoolhouse.btinternet.co.uk/page07/sblock.htm Group 1 Alkali Metals and Group 2 Alkaline Earth Metals], Doc Brown's Chemistry Clinic.
* [http://scienceaid.co.uk/chemistry/fundamental/group2.html Science aid: Group 2 Metals] Study aid for teens
* Hogan, C.Michael. 2010. [http://www.eoearth.org/article/Calcium?topic=49557 ''Calcium''. eds. A.Jorgensen, C. Cleveland. Encyclopedia of Earth]. National Council for Science and the Environment.
* Maguire, Michael E. "Alkaline Earth Metals." ''Chemistry: Foundations and Applications''. Ed. [[J. J. Lagowski]]. Vol. 1. New York: Macmillan Reference USA, 2004. 33-34. 4 vols. Gale Virtual Reference Library. Thomson Gale.
* Silberberg, M.S., Chemistry: The molecular nature of Matter and Change (3e édition, McGraw-Hill 2009)
* Petrucci R.H., Harwood W.S. et Herring F.G., General Chemistry (8e édition, Prentice-Hall 2002)

{|style="text-align: center;" border="1" cellpadding="2"
|+ '''Explanation of above periodic table slice:'''
| bgcolor="{{element color/Alkaline earth metals}}" | Alkaline earth metals
| Atomic numbers in <font color="{{element color/Solid}}">{{element color/Solid}}</font> indicate solids
| style="border:{{element frame/Primordial}};" | Solid borders indicate [[primordial element]]s (older than the [[Earth]])
| style="border:{{element frame/Natural radio}};" | Dashed borders indicate natural [[radioactive decay|radioactive element]]s with no isotopes older than the Earth
|}
{{PeriodicTablesFooter}}
{{compact periodic table}}
{{Alkaline earth metals}}

{{DEFAULTSORT:Alkaline Earth Metal}}
[[Category:Periodic table]]
[[Category:Alkaline earth metals]]

[[af:Aardalkalimetale]]
[[ar:فلز قلوي ترابي]]
[[an:Alcalinoterrio]]
[[ast:Alcalinoterreu]]
[[bn:মৃৎ ক্ষার ধাতু]]
[[bg:Алкалоземен метал]]
[[bs:Zemnoalkalni metali]]
[[ca:Alcalinoterri]]
[[cv:Сĕлтĕ çĕр металлĕсем]]
[[cs:2. skupina]]
[[cy:Metel daear alcalïaidd]]
[[da:Jordalkalimetal]]
[[de:Erdalkalimetalle]]
[[et:Leelismuldmetallid]]
[[el:Αλκαλικές γαίες]]
[[es:Alcalinotérreo]]
[[eo:Teralkala metalo]]
[[eu:Metal lurralkalino]]
[[fa:فلزهای قلیایی خاکی]]
[[hif:Khaara matti dhaatu]]
[[fr:Métal alcalino-terreux]]
[[gl:Alcalinotérreo]]
[[gu:આલ્ક્લાઇન પાર્થિવ ધાતુ]]
[[ko:알칼리 토금속]]
[[hi:क्षारीय पार्थिव धातु]]
[[hr:Zemnoalkalijski metali]]
[[id:Logam alkali tanah]]
[[ia:Metallo alcalin terrose]]
[[is:Jarðalkalímálmur]]
[[it:Metalli alcalino terrosi]]
[[he:מתכת אלקלית עפרורית]]
[[jv:Alkali tanah]]
[[ka:ტუტემიწა ლითონები]]
[[sw:Metali za udongo alikalini]]
[[ht:Metal alkaline-tere]]
[[la:Metalla alcalica terrena]]
[[lv:Sārmzemju metāli]]
[[jbo:mlijilkle]]
[[lmo:Metai alcalitt-teros]]
[[hu:Alkáliföldfémek]]
[[mk:Земноалкален метал]]
[[ml:ആൽക്കലൈൻ എർത്ത് ലോഹങ്ങൾ]]
[[mr:अल्कमृदा धातू]]
[[ms:Logam alkali bumi]]
[[nl:Aardalkalimetaal]]
[[ja:第2族元素]]
[[no:Jordalkalimetall]]
[[nn:Jordalkalimetall]]
[[nds:Eerdalkalimetall]]
[[pl:Berylowce]]
[[pt:Metal alcalinoterroso]]
[[ro:Metal alcalino-pământos]]
[[qu:Allpa alkali q'illay]]
[[ru:Щёлочноземельные металлы]]
[[sah:Алкалин сир метал]]
[[sq:Grupi i dytë i elementeve kimike]]
[[simple:Alkaline earth metal]]
[[sk:Kov alkalických zemín]]
[[sl:Zemljoalkalijska kovina]]
[[sr:Земно-алкални метали]]
[[sh:Zemnoalkalijski metali]]
[[fi:Maa-alkalimetalli]]
[[sv:Alkalisk jordartsmetall]]
[[ta:காரக்கனிம மாழைகள்]]
[[te:క్షారమృత్తిక లోహము]]
[[th:โลหะแอลคาไลน์เอิร์ท]]
[[tr:Alkalin]]
[[uk:Лужноземельні метали]]
[[vi:Kim loại kiềm thổ]]
[[zh:碱土金属]]