View source for Alkaline earth metal



{| align="right" style="margin:0 0 1em 1em;"
! [[Periodic table group|Group]]
! 2
|-
! [[Periodic table period|Period]]
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
|-
! [[Period 2 element|2]]
| {{element cell| 4|Beryllium|Be| |Solid|Alkaline earth metals|Primordial}}
|-
! [[Period 3 element|3]]
| {{element cell|12|Magnesium|Mg| |Solid|Alkaline earth metals|Primordial}}
|-
! [[Period 4 element|4]]
| {{element cell|20|Calcium|Ca| |Solid|Alkaline earth metals|Primordial}}
|-
! [[Period 5 element|5]]
| {{element cell|38|Strontium|Sr| |Solid|Alkaline earth metals|Primordial}}
|-
! [[Period 6 element|6]]
| {{element cell|56|Barium|Ba| |Solid|Alkaline earth metals|Primordial}}
|-
! [[Period 7 element|7]]
| {{element cell|88|Radium|Ra| |Solid|Alkaline earth metals|Natural radio}}
|}

The '''alkaline earth  metals''' are a [[chemical series|series]] of [[chemical element|elements]] comprising [[Periodic table group|Group 2]] ([[IUPAC]] style) of the [[periodic table]]: [[beryllium]] ('''Be'''), [[magnesium]] ('''Mg'''), [[calcium]] ('''Ca'''), [[strontium]] ('''Sr'''), [[barium]] ('''Ba''') and [[radium]] ('''Ra'''). The alkaline earth metals provide a good example of group trends in properties in the periodic table, with well characterised homologous behaviour down the group.

The alkaline earth metals are silvery 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 strongly [[alkali|alkaline]] ([[base (chemistry)|basic]]) [[hydroxide]]s. For example, where [[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 outermost shell, so the energetically preferred state of achieving a filled [[electron shell]] is to lose two electrons to form doubly [[electric charge|charged]] [[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|350px|left|The 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 generally 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 such as modern day batteries, 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. They generally have no natural role in biological systems, (perhaps the only documented example is the primitive marine organism ''[[Acantharea]]'', which uses strontium sulphate to build its [[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" />

==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
*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.



{|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}}

[[Category:Periodic table]]
[[Category:Alkaline earth metals]]

[[af:Aardalkalimetale]]
[[ar:فلز قلوي ترابي]]
[[ast:Alcalinoterreu]]
[[bn:মৃৎ ক্ষার ধাতু]]
[[bg:Алкалоземен метал]]
[[ca:Alcalinoterri]]
[[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:فلز قلیایی خاکی]]
[[fr:Métal alcalino-terreux]]
[[gl:Alcalinotérreo]]
[[ko:알칼리 토금속]]
[[hr:Zemnoalkalijski metali]]
[[id:Logam alkali tanah]]
[[is:Jarðalkalímálmur]]
[[it:Metalli alcalino terrosi]]
[[he:מתכת אלקלית עפרורית]]
[[sw:Metali za udongo alikalini]]
[[lv:Sārmzemju metāli]]
[[jbo:mlijilkle]]
[[lmo:Metàj alcalítt-teruus]]
[[hu:Alkáliföldfém]]
[[mk:Земноалкален метал]]
[[ms:Logam bumi beralkali]]
[[nl:Aardalkalimetaal]]
[[ja:第2族元素]]
[[no:Jordalkalimetall]]
[[nn:Jordalkalimetall]]
[[nds:Eerdalkalimetall]]
[[pl:Metale ziem alkalicznych]]
[[pt:Metal alcalino-terroso]]
[[qu:Allpa alkali q'illay]]
[[ru:Щёлочноземельные металлы]]
[[simple:Alkaline earth metal]]
[[sk:Kovy alkalických zemín]]
[[sl:Alkalijska zemeljska kovina]]
[[sr:Земно-алкални метали]]
[[sh:Zemnoalkalijski metali]]
[[fi:Maa-alkalimetalli]]
[[sv:Alkalisk jordmetall]]
[[ta:காரக்கனிம மாழைகள்]]
[[te:క్షారమృత్తిక లోహము]]
[[th:โลหะแอลคาไลน์เอิร์ท]]
[[vi:Kim loại kiềm thổ]]
[[tr:Alkalin]]
[[uk:Лужноземельні метали]]
[[zh:碱土金属]]

{{jb1}}
{{WikiDoc Help Menu}}
{{WikiDoc Sources}}