Chemistry

An Overview about the Chemical Element Manganese



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Manganese

Symbol: Mn

Atomic Number: 25

Atomic Mass: 54.93805 amu (atomic mass units)

Melting Point: 1245.0 C (1518.15 K, 2273.0 F)

Boiling Point: 1962.0 C (2235.15 K, 3563.6 F)

Number of Protons: 25

Number of Electrons: 25

Number of Neutrons: 30

Classification: Transition Metal

Crystal Structure: Cubic

Density @ 293 K: 7.43 grams per cubic centimeter

Color: silver/gray

The element manganese was proposed to exist by Carl Wilhelm Scheele in1774. Later the same year, the Swedish chemist, Johan Gottlieb Gahn actually discovered the element in the mineral ore pyrolusite. This mineral contains manganese oxide and when heated with charcoal releases manganese and carbon dioxide. The mineral gets its name from the Latin word for magnet "mangnes".

The pure metal is harder than iron and very brittle. Manganese is quite reactive and will decompose slowly in cold water.

Manganese is an essential trace element biologically. It is thought to be required for the metabolism of Vitamin B.

Pure manganese is not found naturally but the element is found as an oxide, silicate or carbonate in many rocks. Manganese dioxide, the most common of its compounds, makes up 0.14% of the Earths' crust. Nodules discovered on the ocean floor have been found to contain 24% manganese and these may prove to be an important source of the element in the future.

Manganese has only one stable isotope, manganese-55. Nearly thirty unstable isotopes of this element have been found most of which decay by beta decay although electron capture and neutron emission decay modes are also seen. Manganese-45 has the shortest half life at less than 70 nanoseconds, it decays by proton emission.

Most of the world's supply still comes from the mineral pyrolusite. Rather than heating with carbon, as in its initial discovery, production of manganese today involves burning the mineral in an oven with powdered aluminum. An alternative method is to treat pyrolusite with sulfuric acid to form manganese sulfate which is then electrolyzed.

Manganese has a number of industrial uses with nearly 90% of the worlds' production being used by the steel industry.

* It is used to remove sulfur and oxygen from molten steel.

* Alloyed to steel it improves strength and makes it easier to work. The steel used to make railway tracks can contain up to 1.2% manganese.

* In the glass industry it is used to impart an amethyst color to glass. It is, in fact, responsible for the color of the amethyst gem stone.

The compound manganese dioxide is also commercially important.

* It is used in dry cell batteries where it prevents the formation of hydrogen gas bubbles.

* It is used as a drying agent in black paints.

* The glass industry uses it to remove the yellow discoloration caused by contamination by iron.

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