Molybdenum was discovered in 1778 by Swedish chemist Carl Wilhelm Scheele, who identified it as a distinct element from a mineral that had been confused with graphite and lead ore. The element was isolated in 1781 by Peter Jacob Hjelm through the reduction of molybdenum(VI) oxide with carbon. The name “molybdenum” comes from the Greek word ‘molybdos’, which means lead, reflecting the mineral’s mistaken identity.
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- Symbol: Mo
- Atomic Number: 42
- Atomic Weight: 95.95
- Element Classification: Transition Metal
- Discovered By: Carl Wilhelm Scheele
- Discovery Date: 1778
- Name Origin: Greek: ‘molybdos’ meaning lead
- Density(g/cc): 10.28
- Melting Point: 2623°C
- Boiling Point: 4639°C
- Appearance: Gray metal, with a very high melting point
- Atomic Radius(pm): 139
Relation to Other Elements
Molybdenum is a transition metal, located in group 6 of the periodic table, between chromium and tungsten. Like other transition metals, it is characterized by its high melting point, strength, and resistance to corrosion. Molybdenum’s ability to form stable compounds in various oxidation states, particularly +4 and +6, makes it versatile in chemical reactions. It shares many physical and chemical properties with tungsten, its heavier homologue, but molybdenum is more abundant and less dense.
Natural Occurrence
Molybdenum is not found free in nature but occurs in various minerals, primarily molybdenite (MoS₂), which is the largest source of the element. Other minerals include powellite (CaMoO₄) and wulfenite (PbMoO₄). Molybdenum is also recovered as a byproduct of copper and tungsten mining. It is relatively abundant in the Earth’s crust and is found in trace amounts in the human body, where it is essential for the functioning of certain enzymes.
Uses
Molybdenum has a wide range of applications due to its unique properties:
- Steel Production: The largest use of molybdenum is as an alloying agent in steel to increase hardness, strength, electrical conductivity, and resistance to wear and corrosion. High-speed steels, which contain significant amounts of molybdenum, are used in cutting tools and drills.
- Chemical Industry: Molybdenum compounds are used as catalysts in the petroleum industry, especially in the process of removing sulfur from natural gas and petroleum products.
- Electronics: Molybdenum is used in the production of semiconductor devices and as electrodes in glass furnaces.
- Aerospace and Defense: Alloys containing molybdenum are used in aircraft parts, missiles, and armor plating due to their high-temperature strength and toughness.
- Medicine: Molybdenum is used as a radiocontrast agent in medical imaging to enhance the contrast of images.
The discovery of molybdenum and the development of its applications have significantly impacted materials science, particularly in the advancement of alloys and catalysis. Its role in enhancing the properties of steel and other metals underscores the importance of transition metals in modern technology and industry.