Alkaline earth metal

The alkaline earth metals are a 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, low-density 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 ions.

The alkaline earth metals are named after their 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 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.