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Magnesium is one of the alkaline-earth metals, and is one of the most common elements in the Earth's crust. In its pure form, it is silvery white, and relatively soft. It burns in air with a brilliant white light, and for this reason is often used in flares and fireworks.
2Mg(s) + O2(g) ——> 2MgO(s)
The high temperatures reached during the combustion also allow small amounts of magnesium to react with nitrogen in the air, producing magnesium nitride:
3Mg(s) + N2(g) ——> 2Mg3N2(s)
Magnesium also burns in an environment of carbon dioxide such as in a beaker full of dry ice:
2Mg(s) + CO2(g) ——> 2MgO(s) + C(s)
Magnesium is used in disposable flash bulbs to generate light for photography, but this use has been largely supplanted by other sources of illumination.
In the demonstration below, a strip of magnesium ribbon is ignited with a Bunsen burner:
Video Clip: REAL, 1.41 MB
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!!! Hazards !!!
In addition to being extremely bright, burning magnesium produces some ultraviolet light; avoid looking directly at it.
The burning magnesium is very hot; do not touch it or let it come in contact with other flammable materials.
Since magnesium burns in the presence of carbon dioxide, a CO2 fire extinguisher does not put out the flame from burning magnesium; a dry-chemical fire extinguisher must be used instead.
Procedures
Magnesium in air: Bassam Z. Shakhashiri, Chemical Demonstrations: A Handbook for Teachers of Chemistry, Volume 1. Madison: The University of Wisconsin Press, 1983, p. 38-39.
Magnesium in carbon dioxide: Lee R. Summerlin, Christie L. Borgford, and Julie B. Ealy, Chemical Demonstrations: A Sourcebook for Teachers, Volume 2, 2nd ed. Washington, D.C.: American Chemical Society, 1988, p. 58.
References
F. Albert Cotton and Geoffrey Wilkinson, Advanced Inorganic Chemistry, 5th ed. New York: John Wiley & Sons, 1988, p. 152-153.
John Emsley, The Elements, 3rd ed. Oxford, Clarendon Press, 1998, p. 120-121.
David L. Heiserman, Exploring Chemical Elements and their Compounds. New York: TAB Books, 1992, p. 49-53.
Martha Windholz (ed.), The Merck Index, 10th ed. Rahway: Merck & Co., Inc., 1983.