Alkaline earth metal
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| Group | 2 |
|---|---|
| Period | |
| 2 | 4 Be |
| 3 | 12 Mg |
| 4 | 20 Ca |
| 5 | 38 Sr |
| 6 | 56 Ba |
| 7 | 88 Ra |
The alkaline earth metals are a series of elements comprising 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 metals, which react readily with halogens to form ionic salts, and with water, though not as rapidly as the alkali metals, to form strongly alkaline (basic) hydroxides. For example, where sodium and potassium react with water at room temperature, magnesium reacts only with steam and calcium with hot water:
- Mg + 2 H2O → Mg(OH)2 + H2
Beryllium is an exception: It does not react with water or steam, and its halides are covalent.
All the alkaline earth metals have two electrons in their outermost shell, so the energetically preferred state of achieving a filled electron shell is to lose two electrons to form doubly charged positive ions.
The alkaline earth metals are named after their oxides, the alkaline earths, whose old-fashioned names were beryllia, magnesia, 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 compounds 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
- 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. bones).
- 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 meals" in radiographic imaging, whilst strontium compounds are employed in some toothpastes.
- Radium has a low availability and is highly radioactive, making it toxic to life.
References
- Group 2 - Alkaline Earth Metals, Royal Chemistry Society.
- Group 1 Alkali Metals and Group 2 Alkaline Earth Metals, Doc Brown's Chemistry Clinic.
- 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.
| Alkaline earth metals | Atomic numbers in black indicate solids | Solid borders indicate primordial elements (older than the Earth) | Dashed borders indicate natural radioactive elements with no isotopes older than the Earth |
Periodic tables | |
|---|---|
| Layouts | Standard · Vertical · Full names · Names and atomic masses · Text for last · Huge table · Metals and nonmetals · Blocks · Valences · Inline f-block · 218 elements · Electron configurations · Atomic masses · Electronegativities · Alternatives |
| Lists of elements | Name · Atomic symbol · Atomic number · Boiling point · Melting point · Density · Atomic mass |
| Groups | 1 · 2 · 3 · 4 · 5 · 6 · 7 · 8 · 9 · 10 · 11 · 12 · 13 · 14 · 15 · 16 · 17 · 18 |
| Periods: | 1 · 2 · 3 · 4 · 5 · 6 · 7 · 8 |
| Series | Alkalis · Alkaline earths · Lanthanides · Actinides · Transition metals · Poor metals · Metalloids · Nonmetals · Halogens · Noble gases |
| Blocks | s-block · p-block · d-block · f-block · g-block |
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 γαίεςeo: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:Eerdalkalimetallqu:Allpa alkali q'illaysimple: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 thổuk:Лужноземельні метали
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
