Stable Isotopes of Manganese
|Isotope||Z(p)||N(n)||Atomic Mass||Natural Abundance||Nuclear Spin|
Manganese was discovered in 1774 by Johann Gahn. Its name originates with the Latin word magnes, meaning "magnet," or magnesia nigri, meaning "black magnesia."
There are four allotropic forms of manganese: The alpha form has a cubic crystal structure and a density of 7.43 g/cm3 and is brittle. It transforms to beta form at 720 ºC. Beta manganese is brittle and has a cubic lattice structure with a density of 7.29 g/cm3 and transforms to gamma form at 1100 ºC, or back to alpha form on cooling. The gamma form exists as a face-centered cubic crystal with a density of 7.18 g/cm3 and converts to the delta form at 1136 ºC. Delta manganese consists of body-centered cubic crystals with a density of 6.30 g/cm3 and is stable up to 1244 ºC, above which it melts to liquid.
Manganese decomposes in water and dissolves readily in dilute mineral acids. Many chemical properties of manganese are similar to those of iron. Manganese burns in air or oxygen at elevated temperatures, forming trimanganese tetroxide. Reactions with concentrated acids are slow at room temperature but rapid when heated. No hydrogen forms in concentrated acids, but sulfur dioxide and nitric oxide form with concentrated sulfuric and nitric acids. Manganese combines with several metals at elevated temperatures, forming binary compounds in varying compositions.
Manganese is distributed broadly in nature — mostly as oxide, silicate, and carbonate ores — and does not occur naturally in its native form. Manganese is used widely in industry, most importantly in ferrous metallurgy. It is also used in chemical, electrochemical, food and pharmaceutical applications. Almost all aluminum and magnesium alloys contain manganese. It is an essential element for all plants and animals; its shortage in soil can cause chlorosis, or lack of chlorophyll, in plants. Its shortage in animals can cause bone deformities. In chemical industries, manganese is used to prepare several compounds. It is also used as a catalyst. Its salts have numerous applications in oxidation, catalysis and medicine.
Properties of Manganese
|Standard state||Solid at 298 °K|
|CAS Registry ID||7439-96-5|
|Group in periodic table||7|
|Period in periodic table||4|
|Block in periodic table||d-block|
|Melting point||1244 °C|
|Boiling point||1962 °C|
|Thermal conductivity||7.81 W/(m·K) at 298.2 °K|
|Electrical resistivity||185.0 µΩ·cm at 25 °C|
0.48 kJ/kg K
|Heat of vaporization||220 kJ·mol-1|
|Heat of fusion||13.2 kJ·mol-1|
|Density of solid||7.21-7.44 g/cm3|
|Atomic radius||1.27 Å|
|Oxidation states||0, +1, +2, +3, +4, +5, +6, +7|
|Most common oxidation states||+2, +4, +7|