Magnesium

Magnesium - Mg

Symbol: Mg
Atomic Number: 12
Atomic Weight: 24.305
Element Classification: Alkaline-earth Metal
Discovered By: Sir Humphrey Davy
Discovery Date: 1808 (England)
Name Origin: Magnesia, ancient city in district of Thessaly, Greece.

Density (g/cc): 1.738
Melting Point (°K): 922
Boiling Point (°K): 1363
Appearance: Lightweight, malleable, silvery-white metal
Atomic Radius (pm): 160
Atomic Volume (cc/mol): 14.0
Covalent Radius (pm): 136
Ionic Radius: 66 (+2e)
Specific Heat (@20°C J/g mol): 1.025
Fusion Heat (kJ/mol): 9.20
Evaporation Heat (kJ/mol): 131.8
Thermal Conductivity (@25°C W/m K):
Debye Temperature (°K): 318.00
Pauling Negativity Number: 1.31
First Ionizing Energy (kJ/mol): 737.3
Oxidation States: 2
Electronic Configuration: [Ne] 3s2
Lattice Structure: Hexagonal (HEX)
Lattice Constant (Å): 3.210
Lattice C/A Ratio: 1.624

Mineral hardness [no units]: 2.5
Hardness [/MN m-2]: 260

Note: Preparation of magnesium and its alloys is rather difficult due to the low matrix hardness and the higher hardness of precipitate phases that lead to relief problems, and from the reactivity of the metal. Mechanical twinning may result during cutting, grinding, or handling if pressures are excessive. Final polishing and cleaning operations should avoid or minimize the use of water and a variety of solutions have been proposed. Pure magnesium is attacked slowly by water while Mg alloys may exhibit much higher attack rates. Some authors state that water should not be used in any step and they use a 1 to 3 mixture of glycerol to ethanol as the coolant even in the grinding steps. Always grind with a coolant, as fine Mg dust is a fire hazard. Because of the presence of hard intermetallic phases, relief may be difficult to control, especially if napped cloths are used.