Molybdenum (42)

Molybdenum (MO-LIB-DEN-UM) is a silvery-white, hard, transition metal. Scheele discovered it in 1778. It was often confused with graphite and lead ore. Molybdenum is used in alloys, electrodes and catalysts. The World War 2 German artillery piece called "Big Bertha" contains molybdenum as an essential component of its steel.

•Name: Molybdenum
•Symbol: Mo
•Atomic number: 42
•Atomic weight: 95.96
•Standard state: solid at 298 K
•CAS Registry ID: 7439-98-7
•Group in periodic table: 6
•Period in periodic table: 5
•Block in periodic table: d-block
•Color: grey metallic
•Classification: Metallic

Historical information

Molybdenum was discovered by Carl William Scheele at 1781 in Sweden. Origin of name is from the Greek word "molybdos" meaning "lead". In 1778 Carl Welhelm Scheele conducted research on an ore now known as molybdenite. He concluded that it did not contain lead as was suspected at the time and reported that the mineral contained a new element that he called molybdenum after the mineral. Molybdenum metal was prepared in an impure form in 1782 by Peter Jacob Hjelm.

Physical properties

•Melting point: 2896 [or 2623 °C (4753 °F)] K
•Boiling point: 4912 [or 4639 °C (8382 °F)] K
•Density of solid: 10280 kg m-3

Orbital properties

•Ground state electron configuration: [Kr].4d5.5s1
•Shell structure: 2.8.18.13.1
•Term symbol: 7S3

Isolation

It is not normally necessary to make samples of molybdenum metal in the laboratory since it is readily available commercially. Industrially, its extraction is sometimes linked to copper production. The normal process is for the sulfide MoS2 to be "roasted" to form the oxide MoO3. This is often used directly in the steel industry.

Pure samples of the metal are available by first dissolving the oxide in ammonium hydroxide to make ammonium molybdate, (NH4)2[MO4], and then reduction of the molybdate with hydrogen gas to form the metal.