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Manganese
Atomic Number: 25
Symbol: Mn
Atomic Weight: 54.93805
Discovery: Johann Gahn, Scheele, & Bergman 1774 (Sweden)
Electron Configuration: [Ar]4s2 3d5
Word Origin: Latin magnes: magnet, referring to the magnetic properties of pyrolusite; Italian manganese: corrupt form of magnesia
Properties: Manganese has a melting point of 1244+/-3°C, boiling point of 1962°C, specific gravity of 7.21 to 7.44 (depending on allotropic form), and valence of 1, 2, 3, 4, 6, or 7. Ordinary manganese is a hard and brittle gray-white metal. It is chemically reactive and slowly decomposes cold water. Manganese metal is ferromagnetic (only) after special treatment. There are four allotropic forms of manganese. The alpha form is stable at normal temperatures. The gamma form changes to the alpha form at ordinary temperature. In contrast to the alpha form, the gamma form is soft, flexible, and easily cut.
Uses: Manganese is an important alloying agent. It is added to improve the strength, toughness, stiffness, hardness, wear resistance, and hardenability of steels. Together with aluminum and antimony, especially in the presence of copper, it forms highly ferromagnetic alloys. Manganese dioxide is used as a depolarizer in dry cells and as a decolorizing agent for glass that has been colored green due to iron impurities. The dioxide is also used in drying black paints and in the preparation of oxygen and chlorine. Manganese colors glass an amethyst color and is the coloring agent in natural amethyst. The permanganate is used as an oxidizing agent and is useful for qualitatitive analysis and in medicine. Manganese is an important trace element in nutrition, although exposure to the element is toxic in higher quantities.
Sources: In 1774, Gahn isolated manganese by reducing its dioxide with carbon. The metal may also be obtained by electrolysis or by reducing the oxide with sodium, magnesium, or aluminum. Manganese-containing minerals are widely distributed. Pyrolusite (MnO2) and rhodochrosite (MnCO3) are among the most common of these minerals.
Element Classification: Transition Metal
Density (g/cc): 7.21
Melting Point (K): 1517
Boiling Point (K): 2235
Appearance: Hard, brittle, grayish-white metal
Atomic Radius (pm): 135
Atomic Volume (cc/mol): 7.39
Covalent Radius (pm): 117
Ionic Radius: 46 (+7e) 80 (+2e)
Specific Heat (@20°C J/g mol): 0.477
Fusion Heat (kJ/mol): (13.4)
Evaporation Heat (kJ/mol): 221
Debye Temperature (K): 400.00
Pauling Negativity Number: 1.55
First Ionizing Energy (kJ/mol): 716.8
Oxidation States: 7, 6, 4, 3, 2, 0, -1
Lattice Structure: Cubic
Lattice Constant (Å): 8.890
References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange's Handbook of Chemistry (1952), CRC Handbook of Chemistry & Physics (18th Ed.)
Atomic Number: 25
Symbol: Mn
Atomic Weight: 54.93805
Discovery: Johann Gahn, Scheele, & Bergman 1774 (Sweden)
Electron Configuration: [Ar]4s2 3d5
Word Origin: Latin magnes: magnet, referring to the magnetic properties of pyrolusite; Italian manganese: corrupt form of magnesia
Properties: Manganese has a melting point of 1244+/-3°C, boiling point of 1962°C, specific gravity of 7.21 to 7.44 (depending on allotropic form), and valence of 1, 2, 3, 4, 6, or 7. Ordinary manganese is a hard and brittle gray-white metal. It is chemically reactive and slowly decomposes cold water. Manganese metal is ferromagnetic (only) after special treatment. There are four allotropic forms of manganese. The alpha form is stable at normal temperatures. The gamma form changes to the alpha form at ordinary temperature. In contrast to the alpha form, the gamma form is soft, flexible, and easily cut.
Uses: Manganese is an important alloying agent. It is added to improve the strength, toughness, stiffness, hardness, wear resistance, and hardenability of steels. Together with aluminum and antimony, especially in the presence of copper, it forms highly ferromagnetic alloys. Manganese dioxide is used as a depolarizer in dry cells and as a decolorizing agent for glass that has been colored green due to iron impurities. The dioxide is also used in drying black paints and in the preparation of oxygen and chlorine. Manganese colors glass an amethyst color and is the coloring agent in natural amethyst. The permanganate is used as an oxidizing agent and is useful for qualitatitive analysis and in medicine. Manganese is an important trace element in nutrition, although exposure to the element is toxic in higher quantities.
Sources: In 1774, Gahn isolated manganese by reducing its dioxide with carbon. The metal may also be obtained by electrolysis or by reducing the oxide with sodium, magnesium, or aluminum. Manganese-containing minerals are widely distributed. Pyrolusite (MnO2) and rhodochrosite (MnCO3) are among the most common of these minerals.
Element Classification: Transition Metal
Density (g/cc): 7.21
Melting Point (K): 1517
Boiling Point (K): 2235
Appearance: Hard, brittle, grayish-white metal
Atomic Radius (pm): 135
Atomic Volume (cc/mol): 7.39
Covalent Radius (pm): 117
Ionic Radius: 46 (+7e) 80 (+2e)
Specific Heat (@20°C J/g mol): 0.477
Fusion Heat (kJ/mol): (13.4)
Evaporation Heat (kJ/mol): 221
Debye Temperature (K): 400.00
Pauling Negativity Number: 1.55
First Ionizing Energy (kJ/mol): 716.8
Oxidation States: 7, 6, 4, 3, 2, 0, -1
Lattice Structure: Cubic
Lattice Constant (Å): 8.890
References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange's Handbook of Chemistry (1952), CRC Handbook of Chemistry & Physics (18th Ed.)
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