Molybdenum (Mo)
Stable isotopes of molybdenum available from ISOFLEX
| Isotope | Z(p) | N(n) | Atomic Mass | Natural Abundance | Enrichment Level | Chemical Form |
| Mo-92 | 42 | 50 | 91.906810 | 14.77% | 75.00-98.70% | Metal |
| Mo-92 | 42 | 50 | 91.906810 | 14.77% | 75.00-98.70% | Oxide |
| Mo-94 | 42 | 52 | 93.905087 | 9.23% | >98.00% | Metal |
| Mo-94 | 42 | 52 | 93.905087 | 9.23% | >98.00% | Oxide |
| Mo-95 | 42 | 53 | 94.905841 | 15.90% | ≥94.30% | Metal |
| Mo-95 | 42 | 53 | 94.905841 | 15.90% | ≥94.30% | Oxide |
| Mo-96 | 42 | 54 | 95.904678 | 16.68% | >95.00% | Metal |
| Mo-96 | 42 | 54 | 95.904678 | 16.68% | >95.00% | Oxide |
| Mo-97 | 42 | 55 | 96.906020 | 9.56% | ≥96.60% | Metal |
| Mo-97 | 42 | 55 | 96.906020 | 9.56% | ≥96.60% | Oxide |
| Mo-98 | 42 | 56 | 97.905407 | 24.19% | >98.40% | Metal |
| Mo-98 | 42 | 56 | 97.905407 | 24.19% | >98.40% | Oxide |
| Mo-100 | 42 | 58 | 99.907477 | 9.67% | 90.00-99.86% | Metal |
| Mo-100 | 42 | 58 | 99.907477 | 9.67% | 90.00-99.86% | Oxide |
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Molybdenum was discovered in 1781 by Carl William Scheele. Its name originates with the Greek word molybdos, meaning “lead.” It does not occur free in nature, and it is a necessary trace element in plant nutrition.
Molybdenum is a silvery-white metal or grayish-black powder with a cubic crystalline structure. It has high strength at very high temperatures and oxidizes rapidly above 1000 °F in air at sea level, but it is stable in an upper atmosphere. It is insoluble in hydrochloric or hydrofluoric acids, ammonia, sodium hydroxide, water or dilute sulfuric acid, and soluble in hot concentrated sulfuric or nitric acids. At ordinary temperatures, molybdenum metal is fairly stable to air, water and most mineral acids. The metal shows high resistance to HCl, H2SO4, HF and H3PO4, and most other mineral acids in the absence of any oxidizing agent. However, the metal is attacked by nitric acid and aqua regia.
Molybdenum is very stable to oxygen at ambient temperatures; however, when heated in air or oxygen to red heat, the metal readily converts to trioxide. When bromine vapor is passed over molybdenum metal at 600-700 ºC in an atmosphere of nitrogen, the product is trimeric molybdenum dibromide. The metal has very little affinity for hydrogen, even in a finely divided state. When heated with carbon monoxide at temperatures above 1000 ºC, no carbonyl is obtained, but a thin film of molybdenum carbide forms over the metal. The metal is used as the starting material to prepare many of its salts.
The largest quantities of molybdenum produced are consumed in the steel industry. The metal is incorporated to impart high resistance and hardness to the steel, as well as to improve its mechanical properties. In the chemical industry, molybdenum compounds are used widely in coloring agents and solid lubricants. Molybdenum compounds are also used as catalysts in many oxidation-reduction reactions and in petroleum refining for production of high-octane gasoline.
Properties of Molybdenum
| Name | Molybdenum |
| Symbol | Mo |
| Atomic number | 42 |
| Atomic weight | 95.94 |
| Standard state | Solid at 298° °K |
| CAS Registry ID | 7439-98-7 |
| Group in periodic table | 6 |
| Group name | None |
| Period in periodic table | 5 |
| Block in periodic table | d-block |
| Color | Grey metallic |
| Classification | Metallic |
| Melting point | 2623 °C |
| Boiling point | 4612 °C |
| Vaporization point | 4639 °C |
| Thermal conductivity | 138 W/(m·K) at 298.2 °K |
| Electrical resistivity | 5.0 µΩ·cm at 0 °C |
| Electronegativity | 1.9 |
| Specific heat | 0.25 kJ/kg K |
| Heat of vaporization | 600 kJ·mol-1 at 4612 °C |
| Heat of fusion | 36 kJ·mol-1 |
| Density of liquid | 9.33 g/cm3 at 2623 °C |
| Density of solid | 10.28 g/cm3 |
| Electron configuration | [Kr]4d55s1 |
| Atomic radius | 1.36 Å (coordination number 8) |
| Ionic radius | Mo3+: 0.92 Å and Mo6+: 0.62 Å |
| Oxidation states | 0, +2, +3, +4, +5, +6 |
| Most stable oxidation state | +6 |
| Atomic volume | 9.41 cm3/mol |
