The alkaline earth metals are the elements referred to as group two metals because they are found in group two of the periodic table. These metals have distinct properties that allow them to be grouped together. The metals which make up the group of alkaline earth metals are, from top to bottom, beryllium, magnesium, calcium, strontium, barium and radium.
Natural Occurrences Alkaline Earth Metals
Beryllium is only found combined with other elements in nature. Among its compounds are the gems: aquamarine, which is the turquoise variety of beryl; bixbite, also known as red beryl and emerald, which is green beryl. Beryllium is also a constituent of the gemstones chrysoberyl and phenacite. Beryllium is present in bertrandite, which is one of the main ores of beryllium.
Magnesium is found in over sixty minerals on earth. Among these, only dolomite, magnesite, brucite, carnallite, talc and olivine are of commercial importance.
Magnesium is the fourth most abundant element in the earth's crust where it constitutes only two per cent by mass. Magnesium is the eleventh most abundant element by mass in the human body, playing a major role in the manipulation of phosphate compounds such as ATP.
Magnesium is too reactive to occur naturally in is elementary state.
Calcium occurs naturally in sedimentary rocks such as calcite, dolomite and gypsum. Calcium can also be found in igneous rocks among which is plagioclase and in metamorphic rock such as garnets.
Calcium is a very abundant metal in the earth's crust as well as the human body. Like the other Group Two metals, pure, uncombined calcium does not occur naturally because the metal is too reactive.
Strontium occurs mainly in the form of its carbonate and sulfate naturally. It is more commonly known to exist as a product of nuclear fall out.
Barium, like strontium occurs mainly in the form of its carbonate and sulfate. Barium is also a constituent of the rare blue gemstone, benitoite.
Radium is a radioactive element. It is a decay product of uranium, and so, can be found in uranium ores.
Physical Properties of Alkaline Earth Metals
Alkaline earth metals are silvery, soft, low density metals which tarnish in air. They are so soft that they can be cut with a knife. Compared to other metals further in the periodic table, group two metals have low boiling and melting points. All alkaline earth metals have two valence electrons.
Alkaline earth metals burn in oxygen giving characteristic flames which are unique to each alkaline metal. Beryllium burns with a colorless flame, magnesium with a bright white flame and calcium with a brick red flame. Strontium burns with crimson flame while barium's flame is colored apple green.
Major Uses of Alkaline Earth Metals
Beryllium
Beryllium is primarily used in alloys. Its low densities allows it to add strength to other metals without adding much weight. A very important alloy of beryllium is beryllium copper which is, as expected, a mixture of beryllium and copper, Beryllium copper is used to make tools which are to be used in hazardous environments. Its non-sparking and non magnetic properties allow this. Beryllium copper is also used in the production of some musical instruments such as the tambourine and triangle. Furthermore, Beryllium copper is used in the production of bullets, precision measurement devices and in aerospace.
Magnesium
Like beryllium, magnesium is also used in alloys because it lends strength without adding much weight. Duralumin, an alloy of magnesium, aluminum and copper, is used in the production of air crafts and small boats. Other magnesium alloys are used in the production of household material.
Magnesium is used as flares and distress signals. This use is attributed to the bright white light produced when burning magnesium in oxygen.
Magnesium compounds are also very useful. These include magnesium oxide which is used as a refractory lining material, magnesium sulfate which is used as epson salts, as artificial snow and in fertilizers and magnesium hydroxide which is used as an antacid.
Calcium
Calcium's usefulness is found mainly in its compounds. However, calcium in its elemental form is used in alloys and as a de-oxidizer in steel.
Calcium compounds are especially important to a healthy body. They are involved in the strengthening of bones and teeth and in the transfer of nerve impulses. Calcium compounds are also involved in the control of fertilization in the human body permitting only one sperm to enter the egg.
Plaster of Paris which is used in casts is made of calcium sulfate. Gypsum wallboard, often called plasterboard, is also made of calcium sulfate.
Calcium carbonate, which exists as limestone, chalk, and marble is very important in the construction industry.
Barium
Barium is used in alloys with calcium and lead. Barium sulfate is used in medicine as a 'barium meal'. Patients swallow the sulfate which is relatively opaque to X-Rays and shows particularly well on X-Ray photographs.
Group Two metals, called the alkaline earth metals, have similar properties which allow them to be grouped together. These metals are very useful both in their elemental form and in compounds.
SOURCES
Ramsden, E.N. (2000) A Level Chemistry. Nelson Thornes Ltd.
Hill, G.C., John, H.S (1995) Chemistry in Context. ELBS
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