Molybdenum Chemical & Physical Properties

Molybdenum Chemical & Physical Properties Atomic Number: 42 Symbol: Mo Atomic Weight: 95.94 Discovery: Carl Wilhelm Scheele 1778 (Sweden) Electron Configuration: [Kr] 5s1 4d5 Element Classification: Transition Metal Word Origin: Greek molybdos, Latin molybdoena, German Molybdenum: lead Properties Molybdenum does not occur free in nature; it is usually found in molybdenite ore, MoS2, and wulfenite ore, PbMoO4. Molybdenum is also recovered as a by-product of copper and tungsten mining. It is a silvery-white metal of the chromium group. It is very hard and tough, but it is softer and more ductile than tungsten. It has a high elastic modulus. Of the readily-available metals, only tungsten and tantalum have higher melting points. Uses Molybdenum is an important alloying agent which contributes to the hardenability and toughness of quenched and tempered steels. It also improves the strength of steel at high temperatures. It is used in certain heat-resistant and corrosion-resistant nickel-based alloys. Ferro-molybdenum is used to add hardness and toughness to gun barrels, boilers plates, tools, and armor plate. Almost all ultra-high strength steels contain 0.25% to 8% molybdenum. Molybdenum is used in nuclear energy applications and for missile and aircraft parts. Molybdenum oxidizes at elevated temperatures. Some molybdenum compounds are used to color pottery and fabrics. Molybdenum is used to make filament supports in incandescent lamps and as filaments in other electrical devices. The metal has found application as electrodes for electrically-heated glass furnaces. Molybdenum is valuable as a catalyst in the refining of petroleum. The metal is an essential trace element in plant nutrition. Molybdenum sulfide is u sed as a lubricant, particularly at high temperatures where oils would decompose. Molybdenum forms salts with valencies of 3, 4, or 6, but the hexavalent salts are the most stable. Molybdenum Physical Data Density (g/cc): 10.22 Melting Point (K): 2890 Boiling Point (K): 4885 Appearance: silvery white, hard metal Atomic Radius (pm): 139 Atomic Volume (cc/mol): 9.4 Covalent Radius (pm): 130 Ionic Radius: 62 (6e) 70 (4e) Specific Heat (20Â °C J/g mol): 0.251 Fusion Heat (kJ/mol): 28 Evaporation Heat (kJ/mol): ~590 Debye Temperature (K): 380.00 Pauling Negativity Number: 2.16 First Ionizing Energy (kJ/mol): 684.8 Oxidation States: 6, 5, 4, 3, 2, 0 Lattice Structure: Body-Centered Cubic Lattice Constant (Ã…): 3.150 Sources CRC Handbook of Chemistry Physics, 18th Ed.Crescent Chemical Company, 2001.Langes Handbook of Chemistry, 1952.Los Alamos National Laboratory, 2001.