Molybdenum

Lore & Background

Molybdenite, the principal ore of molybdenum, was historically confused with graphite and the lead ore galena. For the next century, molybdenum had no industrial use due to scarcity, difficulty in extraction, and immature metallurgy. Early molybdenum steel alloys showed promise of increased hardness but were hampered by inconsistent results, brittleness, and recrystallization. Coolidge filed a patent for rendering molybdenum ductile, leading to applications as a heating element.

Reader's Guide

Molybdenum's significance spans multiple fields. Industrially, about 80% of world production is used in steel alloys, including high-strength alloys and superalloys, because it readily forms hard, stable carbides. Approximately 14% of production is used in pigments and catalysts. Biologically, molybdenum is essential for all higher eukaryote organisms, including humans. Molybdenum-bearing enzymes are the most common bacterial catalysts for breaking the chemical bond in atmospheric molecular nitrogen during biological nitrogen fixation. At least 50 molybdenum enzymes are known in bacteria, plants, and animals. Most nitrogenases contain an iron–molybdenum cofactor (FeMoco). In nuclear chemistry, molybdenum-99 is a fission product and parent radioisotope to technetium-99m, used in medical imaging. Molybdenum also acts as a redox buffer in spent nuclear fuel, inhibiting oxidation of uranium dioxide. The element's chemistry shows strong similarities to tungsten, and it forms compounds in oxidation states from −4 to +6, with the most stable being +4 and +6.

Did You Know?

• Molybdenum-99 is a parent radioisotope to technetium-99m, a nuclear isomer used in medical imaging.
• A species of sponge, Theonella conica, is known for hyperaccumulation of molybdenum.
• Molybdenum forms a sextuple bond in its gaseous diatomic species Mo2.