Molybdenum
Element 42 · Transition Metal
Molybdenum is one of the most refractory of all metals, melting at 2623 °C — higher than every element except a handful. That heat resistance, plus its ability to harden steel without making it brittle, makes it essential in armor plate, cutting tools, and furnace parts. Its chemistry is unusually rich: molybdenum appears in oxidation states from +2 to +6, giving colorful compounds and versatile catalysts for petroleum refining. Biology depends on it too — molybdenum sits at the active site of nitrogenase, the enzyme soil bacteria use to convert atmospheric nitrogen into a form plants can use.
Key facts
| Atomic number | 42 |
|---|---|
| Atomic weight | 95.95 |
| Category | Transition Metal |
| Group / Period | 6 / 5 |
| Block | d |
| Electron configuration | [Kr] 4d5 5s1 |
| Common oxidation states | +6, +4, +3, +2 |
| State at STP | Solid |
| Electronegativity | 2.16 |
| Atomic radius | 139 pm (empirical) |
| Density | 10.28 g/cm³ |
| Melting point | 2623 °C |
| Boiling point | 4639 °C |
Occurrence
Molybdenum is mined chiefly from molybdenite (molybdenum disulfide), often recovered as a by-product of copper mining. Major deposits are found in the Americas and China.
Applications
High-strength and stainless steels
Catalysts for petroleum refining
Heating elements and furnace parts
Solid lubricant (molybdenum disulfide)
Common compounds
- Molybdenum disulfide
- Molybdenum trioxide
- Ammonium molybdate
Molybdenum is an essential trace element for almost all life — enzymes that fix nitrogen in soil bacteria cannot work without it.
Data source: IUPAC standard atomic weights 2021; NIST physical property data