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Atomic symbol: Mn |
Atomic number: 25 |
Atomic weight: 54.9380 |
Atomic volume: 1.39 cm3/mol |
Density: 7.43 g/cm3 |
Period Number: 4 |
Group number: 7 |
Group name: Trans. Met. |
Element classification: Metal |
Phase at room temperature: Solid |
Melting Point: 1517.2 K |
Boiling point: 2333 K |
Heat of fusion: 12.050 kJ/mol |
Heat of vaporization: 226.0 kJ/mol |
Ionization Energy: 7.434 eV |
1st ionization energy: 717.4 kJ/mole |
2nd ionization energy: 1509 kJ/mole |
3rd ionization energy: 3248.3 kJ/mole |
Electronegativity: 1.55 |
Electron affinity: kJ/mole |
Specific heat: 0.48 J/gK |
Heat atomization: 281 kJ/mole atoms |
Shells: 2,8,13,2 |
Electron Shell Configuration: [Ar] 3d5 4s2 |
Minimum oxidation number: -3 |
Maximum oxidation number: 7 |
Minimum common oxidation number: 0 |
Maximum common oxidation no: 7 |
Appearance & Characteristics |
Structure:: special:complex (cubic) |
Color: gray-white |
Hardness: 5 mohs |
Toxicity: ? |
Characteristics: hard, brittle |
Uses: steel, dry cells(MnO2) |
Reaction with air: mild, w/ht =>Mn3O4, Mn3N2 |
Reaction with 6M HCl: mild, =>H2, MnCl2 |
Reaction with 15M HNO3: mild, =>Mn(NO3)2, NOx |
Reaction with 6M NaOH: ? |
Number of isotopes: 1 |
Oxide(s): MnO Mn3O4 Mn2O3 MnO2 Mn2O7 |
Hydride(s): none |
Chloride(s): MnCl2 |
Atomic Radius: 127 pm |
Ionic radius (1- ion): pm |
Ionic radius (1+ ion): pm |
Ionic radius (2- ion): pm |
Ionic radius (2+ ion): 89 pm |
Ionic radius (3+ ion): 75.3 pm |
Thermal conductivity: 7.81 J/m-sec-deg |
Electrical conductivity: 5.405 1/mohm-cm |
Polarizability: 9.4 A^3 |
Source: Pyrolusite,psilomelane(oxide) |
Relative abundance solar system: 3.980 log |
Abundance earth's crust: 3 log |
Estimated crustal abundance: 9.50×102 milligrams per kilogram |
Estimated oceanic abundance: 2×10-4 milligrams per liter |
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(L. magnes: magnet, from magnetic properties of pyrolusite; Itl. manganese, corrupt form of magnesia)
Recognized by Scheele, Bergman, and others as an element and isolated by Gahn in 1774 by reduction of the dioxide with carbon.
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Manganese minerals are widely distributed; oxides, silicates, and carbonates are the most common. The discovery of large quantities of manganese nodules on the floor of the oceans may become a source of manganese. These nodules contain about 24% manganese, together with many other elements in lesser abundance.
Most manganese today is obtained from ores found in Russia, Brazil, Australia, South Africa, Gabon, and India. Pyrolusite and rhodochrosite are among the most common manganese minerals. The metal is obtained by reduction of the oxide with sodium, magnesium, aluminum, or by electrolysis.
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It is gray-white, resembling iron, but is harder and very brittle. The metal is reactive chemically, and decomposes cold water slowly. Manganese is used to form many important alloys. In steel, manganese improves rolling and forging qualities, strength, toughness, stiffness, wear resistance, hardness, and hardenability.
With aluminum and antimony, and especially with small amounts of copper, it forms highly ferromagnetic alloys.
Manganese metal is ferromagnetic only after special treatment. The pure metal exists in four allotropic forms. The alpha form is stable at ordinary temperature; gamma manganese, which changes to alpha at ordinary temperatures, is said to be flexible, soft, easily cut, and capable of being bent.
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The dioxide (pyrolusite) is used as a depolarizer in dry cells, and is used to "decolorize" glass that is colored green by impurities of iron. Manganese by itself colors glass an amethyst color, and is responsible for the color of true amethyst. The dioxide is also used in the preparation of oxygen and chlorine, and in drying black paints. The permanganate is a powerful oxidizing agent and is used in quantitative analysis and in medicine.
Manganese is widely distributed throughout the animal kingdom. It is an important trace element and may be essential for utilization of vitamin B1.
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