Magnesium
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a light, silvery-white and shiny alkaline earth metal. Here are some key points about magnesium:
Physical Properties:
- Appearance: Magnesium is a silvery-white metal when freshly cut but quickly tarnishes in air, forming a dull oxide layer.
- Density: It has a density of 1.738 g/cm³, making it less dense than aluminum.
- Melting Point: 650°C (1202°F) and a Boiling Point: of 1091°C (1994°F).
- Hardness: Magnesium is relatively soft, with a hardness of about 2 on the Mohs scale.
Chemical Properties:
- Magnesium is highly reactive, especially when finely divided. It burns with a bright white light, making it useful in fireworks and flares.
- It reacts with water at room temperature, releasing hydrogen gas, but this reaction is slow unless the metal is in a powdered form or the water is hot.
- It forms a variety of compounds, including magnesium oxide (MgO), magnesium hydroxide [Mg(OH)₂], and magnesium carbonate (MgCO₃).
History:
- Magnesium was first identified by Joseph Black in 1755 while he was experimenting with magnesia alba (magnesium carbonate). However, it was not isolated as a metal until 1808 when Humphry Davy electrolyzed a mixture of moist magnesium oxide and mercuric oxide.
- The name "magnesium" comes from the Greek word for a district in Thessaly called Magnesia.
Applications:
- Industry: Magnesium alloys are used in the automotive and aerospace industries due to their low density, high strength-to-weight ratio, and good machinability. Magnesium is also used in die-casting.
- Medical: Magnesium plays a vital role in human health, being essential for over 300 biochemical reactions. It is used in medicine as a mild laxative in the form of magnesium sulfate (Epsom salt) and as an antacid.
- Photography: Historically, magnesium ribbon was used in flash photography because of its bright light when ignited.
- Electrical: Magnesium is used in the production of aluminum alloys, improving their workability and corrosion resistance.
Natural Occurrence:
- Magnesium is the eighth most abundant element in the Earth's crust and the fourth most common element in the Earth as a whole, making up 13% of its mass.
- It is found in large deposits of dolomite, magnesite, and other minerals like carnallite, talc, and asbestos. It also occurs in seawater, where it is the third most abundant element dissolved in it, after sodium and chlorine.
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