The Element Molybdenum
Atomic Number: 42
Atomic Weight: 95.96
Melting Point: 2896 K (2623°C or 4753°F)
Boiling Point: 4912 K (4639°C or 8382°F)
Density: 10.2 grams per cubic centimeter
Phase at Room Temperature: Solid
Element Classification: Metal
Period Number: 5 Group Number: 6 Group Name: none
What's in a name? From the Greek word for lead, molybdos.
Say what? Molybdenum is pronounced as meh-LIB-deh-nem.
History and Uses:
Molybdenum was discovered by Carl Welhelm Scheele, a Swedish chemist, in 1778 in a mineral known as molybdenite (MoS2) which had been confused as a lead compound. Molybdenum was isolated by Peter Jacob Hjelm in 1781. Today, most molybdenum is obtained from molybdenite, wulfenite (PbMoO4) and powellite (CaMoO4). These ores typically occur in conjunction with ores of tin and tungsten. Molybdenum is also obtained as a byproduct of mining and processing tungsten and copper.
Molybdenum has a high melting point and is used to make the electrodes of electrically heated glass furnaces. Some electrical filaments are also made from molybdenum. The metal is used to make some missile and aircraft parts and is used in the nuclear power industry. Molybdenum is also used as a catalyst in the refining of petroleum.
Molybdenum is primarily used as an alloying agent in steel. When added to steel in concentrations between 0.25% and 8%, molybdenum forms ultra-high strength steels that can withstand pressures up to 300,000 pounds per square inch. Molybdenum also improves the strength of steel at high temperatures. When alloyed with nickel, molybdenum forms heat and corrosion resistant materials used in the chemical industry.
Most molybdenum compounds have low water solubility, but the molybdate ion MoO2−4 is soluble and will form if molybdenum-containing minerals are in contact with oxygen and water. Recent theories suggest that the release of oxygen by early life was important in removing molybdenum from minerals into a soluble form in the early oceans, where it was used as a catalyst by single-celled organisms. This sequence may have been important in the history of life, because molybdenum-containing enzymes then became the most important catalysts used by some bacteria to break into atoms the atmospheric molecular nitrogen, allowing biological nitrogen fixation. This, in turn allowed biologically driven nitrogen-fertilization of the oceans, and thus the development of more complex organisms.
At least 50 molybdenum-containing enzymes are now known in bacteria and animals, though only the bacterial and cyanobacterial enzymes are involved in nitrogen fixation. Due to the diverse functions of the remainder of the enzymes, molybdenum is a required element for life in higher organisms (eukaryotes), though not in all bacteria.
Estimated Crustal Abundance: 1.2 milligrams per kilogram
Estimated Oceanic Abundance: 1×10-2 milligrams per liter
Number of Stable Isotopes: 6 (View all isotope data)
Ionization Energy: 7.092 eV
Oxidation State: +6
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Mo
Molybdenum
95.96
Atomic Number: 42
Atomic Weight: 95.96
Melting Point: 2896 K (2623°C or 4753°F)
Boiling Point: 4912 K (4639°C or 8382°F)
Density: 10.2 grams per cubic centimeter
Phase at Room Temperature: Solid
Element Classification: Metal
Period Number: 5 Group Number: 6 Group Name: none
What's in a name? From the Greek word for lead, molybdos.
Say what? Molybdenum is pronounced as meh-LIB-deh-nem.
Estimated Crustal Abundance: 1.2 milligrams per kilogram
Estimated Oceanic Abundance: 1×10-2 milligrams per liter
Number of Stable Isotopes: 6 (View all isotope data)
Ionization Energy: 7.092 eV
Oxidation State: +6
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