Chemistry

An Overview about the Chemical Element Molybdenum



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Molybdenum

Symbol: Mo

Atomic Number: 42

Atomic Mass: 95.94 amu (atomic mass units)

Melting Point: 2617.0 C (2890.15 K, 4742.6 F)

Boiling Point: 4612.0 C (4885.15 K, 8333.6 F)

Number of Protons: 42

Number of Electrons: 42

Number of Neutrons: 54

Classification: Transition Metal

Crystal Structure: Cubic

Density @ 293 K: 10.22 grams per cubic centimeter

Color: silver

Molybdenum was first recognized as a new element in 1778 by the Swedish chemist Carl Wilhelm Scheele. He was looking at a sample of the mineral molybdenite which at that was thought to contain the element lead. He named this new element after the mineral in which it had been found. Molybdenite was named after the Greek word for lead "molybdos". An impure sample of the metal was prepared by Peter Jacob Hjelm in 1782.

There are six naturally occurring stable isotopes of the element molybdenum. The most common of these isotopes and making up 24.13% of the total abundance is molybdenum-98. The others are molybdenum-96 (16.68%), molybdenum-95 (15.92%), molybdenum-92 (14.84%), molybdenum-97 (9.55%) and molybdenum-94 (9.25%). The remaining 9.63% of naturally occurring molybdenum is made up of the unstable molybdenum-100 which has the extremely long half-life of 9.5 quintillion years. Other unstable isotopes of molybdenum have been produced with atomic masses in the range of 83 to 115.

Molybdenum is a very hard silver-white metal. Its most common ore is molybdenite but it is also extracted from wulfenite and powellite. Another source of the metal is as a by-product from the mining and extraction of the metals tin, copper and tungsten.

The element has a number of metallurgical applications and some of its compounds have also proven useful.

* It is used in amounts of between 0.25% and 8% in the production of ultra high strength steels.

* Molybdenum-nickel alloys are very resistant to both heat and chemical corrosion. Such alloys are used in the chemical industry.

* As well as being strong molybdenum is also comparatively light. These factors have made it useful in the production of missiles and aircraft as well as in the nuclear power industry.

* Molybdenum has been used to produce weapons. Swords made in Japan during the fourteenth century have been found to contain molybdenum. "Big Bertha" the German heavy artillery pieces of the First World War also contained the element.

* It is used as a catalyst in the production of petroleum.

* Molybdenum disulfide is used as a high temperature lubricant.

* Molybdenum trioxide is used to make enamels adhere to metals.

* Its high melting point has allowed electrodes made of molybdenum to be used in electrically heated glass furnaces.

Molybdenum is also a biologically necessary element in small quantities. It plays an important part in nitrogen fixation by plants. It is also important in some other enzymatic reactions

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