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Facts About Molybdenum

molybdenum
Electron configuration and elemental properties of molybdenum.
Credit: Greg Robson/Creative Commons, Andrei Marincas | Shutterstock
Atomic Number: 42
Atomic Symbol: Mo
Atomic Weight: 95.96
Melting Point: 4,753 F (2,623 C)
Boiling Point: 8,382 F (4,639 C)

[See Periodic Table of the Elements]

Word origin: The word molybdenum comes from the Greek molybdo, lead.

Discovery: Molybdenum was confused with graphite and lead ore until 1778 when Carl Wilhelm Scheele, a Swedish chemist, recognized it as a distinct element. It was prepared in an impure form in 1782 by Peter Jacob Hjelm.

Properties of molybdenum

Molybdenum is a silvery white and very hard transition metal. It has a high elastic modulus, and only tungsten and tantalum (of the readily available metals) have higher melting points. It is softer and more ductile than tungsten. It oxidizes at elevated temperatures.

Sources of molybdenum

Molybdenum does not occur natively. It is most often obtained from the minerals molybdenite, wulfenite and powellite. Mineral deposits are in Alaska, California, Colorado, Oregon, Utah, Washington, South America, China and elsewhere.

Molybdenite
Molybdenite is the primary source of molybdenum.
Credit: bonchan | Shutterstock

Molybdenum is also recovered as a by-product of tungsten and copper mining operations. It can be prepared from a powder made by the hydrogen reduction of ammonium molybdate or purified molybdic trioxide.

Uses of molybdenum

Molybdenum is a valuable alloying agent, contributing to quenched and tempered steels’ ability to harden and toughness. It also improves the strength of steel at high temperatures. Almost all ultra high-strength steels contain molybdenum. It is used in certain nickel-based alloys, such as the Hastelloys, patented alloys that are resistant to heat and corrosion and chemical solutions.

Recently, molybdenum has been used as electrodes for electrically heated glass furnaces and forehearths. It can also be used in nuclear energy applications, missile and aircraft parts, and as a filament material in electronic and electrical applications. It is a valuable catalyst for refining petroleum.

Molybdenum is an essential trace element in plant nutrition; its absence can cause some land to be barren. As a trace element, molybdenum is necessary for nitrogen fixation and other metabolic processes.

Molybdenum sulfide can be a useful lubricant, especially at high temperatures that would decompose oils.

(Source: Los Alamos National Laboratory)

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