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Magnesium (Mg) is a silvery white metal that resembles aluminium in appearance but weighs one-third less. It is the lightest structural metal known, with a density of only 1.738 grams per cubic centimetre. It has a hexagonal close-packed (hcp) crystalline structure, so it lacks ductility when worked at lower temperatures, as do most metals with this structure. Furthermore, in its pure form, it lacks the strength required for most structural applications. The addition of alloying elements, however, improves its properties to the point where both cast and wrought magnesium alloys are widely used, particularly where light weight and high strength are important.
At high temperatures, magnesium is highly reactive with oxygen; above 645 °C (1,190 °F) in dry air, it burns with a bright white light and intense heat. As a result, magnesium powders are commonly used in pyrotechnics. A stable film of water-insoluble magnesium hydroxide forms on the metal’s surface at room temperature, protecting it from corrosion in most environments. Magnesium, as a strong reactant that forms stable compounds with chlorine, oxygen, and sulphur, has a variety of metallurgical applications, including the production of titanium from titanium tetrachloride and the desulfurization of blast-furnace iron. Its chemical reactivity is also visible in magnesium compounds, which are widely used in industry, medicine, and agriculture.
Chemical Compounds:
Magnesium compounds are a significant group of chemicals. The most well-known medical compounds are milk of magnesia and magnesium hydroxide, which are used as antacids or mineral supplements to keep the body’s magnesium balance in check. MgSO4.7H2O, the hydrous magnesium sulphate commonly known as Epsom salts, is used as a laxative.
Dolomite is used as a fertiliser in areas with acid soil, and magnesium oxide is used as a mineral addition to cattle feed at the start of the grazing season in early spring.
Magnesium compounds are most commonly used in the manufacturing of refractory bricks as magnetite and dolomite. High-purity magnesia bricks are extremely wear- and temperature-resistant, with a high heat capacity and conductivity. The more expensive fused magnesia is used as an insulator in electrically heated stoves and ovens, whereas the less expensive caustic magnesia is a constituent in paper industry leaching lyes, where it reduces losses and allows for the processing of both coniferous and deciduous wood.
Reaction of magnesium with air
Magnesium is a white metal with a silvery lustre. The surface of magnesium metal is covered with a thin layer of oxide, which protects it from air attack. When magnesium metal is ignited, it burns in air with a characteristic blinding bright white flame, producing a mixture of white magnesium oxide, MgO, and magnesium nitride, Mg3N2. Magnesium oxide is typically produced by heating magnesium carbonate. Calcium is more reactive with air than magnesium, which is located immediately below it in the periodic table.
2Mg(s) + O2(g) → 2MgO(s)
3Mg(s) + N2(g) → Mg3N2(s)
Reaction of magnesium with water
Magnesium does not react significantly with water. This is in contrast to calcium, which, in the periodic table, is immediately below magnesium and does react slowly with cold water. Magnesium metal, on the other hand, reacts with steam to produce magnesium oxide (MgO) (or magnesium hydroxide, Mg(OH)2, in the presence of excess steam) and hydrogen gas (H2).
Mg(s) + 2H2O(g) → Mg(OH)2(aq) + H2(g)
Reaction of magnesium with the halogens
Magnesium’s reaction with halogens
Magnesium reacts strongly with halogens such as chlorine, Cl2, and bromine, Br2, and burns to form the dihalides magnesium(II) chloride, MgCl2, and magnesium(II) bromide, MgBr2.
Mg(s) + Cl2(g) → MgCl2(s)
Mg(s) + Br2(g) → MgBr2(s)
Reaction of magnesium with acids
Magnesium metal readily dissolves in dilute sulphuric acid to form solutions containing the aquated Mg(II) ion and hydrogen gas, H2. The Corresponding reactions are the other acids such as hydrochloric acid and produce the aquated Mg(II) ion as well.
Mg(s) + H2SO4(aq) → Mg2+(aq) + SO42-(aq) + H2(g)
Mg(s) + 2HCl(aq) → Mg2+(aq) + 2Cl– (aq) + H2(g)
Conclusion
When magnesium metal is ignited, it burns in air with a characteristic blinding bright white flame, producing a mixture of white magnesium oxide, MgO, and magnesium nitride, Mg3N2. At the high temperatures, magnesium is highly reactive with oxygen; above 645 °C in dry air, it burns with a bright white light and intense heat. The most well-known medical compounds are milk of magnesia and magnesium hydroxide, which are used as antacids or mineral supplements to keep the body’s magnesium balance in check. Dolomite is used as a fertiliser in areas with acid soil, and magnesium oxide is used as a mineral addition to cattle feed at the start of the grazing season in early spring. Magnesium compounds are most commonly used in the manufacturing of refractory bricks as magnetite and dolomite.
