|
History and Production
Drived from the Greek word molybdos, meaning lead. In 1778, C.W. Scheele made the oxide of a new element from the mineral molybdenite (MoS2). However, before then, the mineral was once confused with graphite and lead ore. Four years later, P.J. Hjelm isolated the metal by heating the oxide with charcoal. The metal is obtained commercially from molybdenum ores by flotation and then roasted to give MoO3 which is then dissolved in ammonia to give an ammonium compound. The metal can be subsequently obtained
by hydrogen reduction of the ammonium compound. The latter is also used as a starting point to manufacture other molybdenum compounds. The metal is also recovered as a byproduct of copper and tungsten mining operations.
The metal is used as a catalyst in petrochemical industry and also as electrode material in glass furnaces. The oxide is used in the manufacture of stainless steel and high speed tools which imporves the strength of steel at high temperatures.
Physical Data
The metal is silvery white and very hard. It has a high melting point and elastic modulus. The metal is quite rare, about 1.2 ppm in abundance. The most important ores being molybdenite. It is an essential trace element in plant. In fact, some lands are barren due to the lack of this element in the soils.
Interatomic distance: 272.6 pm
Melting point: 2623°C
Boiling point: 4639°C
Thermal conductivity/Wm-1K-1: 138 (27°C)
Density/kgm-3: 10220 (20°C), 9330 (m.p.)
Standard Thermodynamic Data (atomic gas)
Enthalpy of formation: 658.1 kJ/mol
Gibbs free energy of formation: 612.5 kJ/mol
Entropy: 182 J/mol K
Heat capacity: 20.8 J/mol K
Electronic data
Electronic configuration: [Kr] 4d5 5s1
Term symbol: 7S3
Electron affinity: 72.1711 kJ/mol Electronegativity (Pauline): 2.16
Ionization energy (first, second, third): 684.316, 1559.20, 2617.65 kJ/mol
Chemical properties
| 
