Alkaline earth metal 37411 224107845 2008-07-07T10:11:22Z Nergaal 4761569 {| style="float: right; border: 1px solid #ccc; margin: 0.5em 0pt 0.8em 1.4em; padding: 3px !important; width: 75px;" ! [[Group (periodic table)|Group]]&nbsp;→!! 2 |- ! ↓&nbsp;[[Period (periodic table)|Period]] |- ! [[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 characterized homologous behavior down the group. The alkaline earth metals are silvered 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 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]] [[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, 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 sulfate 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 |} {{compact periodic table}} {{PeriodicTablesFooter}} [[Category:Periodic table]] [[Category:Alkaline earth metals]] {{Link FA|lmo}} [[af:Aardalkalimetale]] [[ar:فلز قلوي ترابي]] [[ast:Alcalinoterreu]] [[bn:মৃৎ ক্ষার ধাতু]] [[bs:Zemnoalkalni metali]] [[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]] [[jv:Alkali tanah]] [[sw:Metali za udongo alikalini]] [[lv:Sārmzemju metāli]] [[jbo:mlijilkle]] [[lmo:Metai alcalitt-teros]] [[hu:Alkáliföldfém]] [[mk:Земноалкален метал]] [[ml:ആല്‍ക്കലൈന്‍ എര്‍ത്ത് ലോഹങ്ങള്‍]] [[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]] [[ro:Metal alcalino-pământos]] [[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]]