Manganese Basic Facts
Atomic Number: 25
Atomic Weight: 54.93805
Discovery: Johann Gahn, Scheele, & Bergman 1774 (Sweden)
Electron Configuration: Ar4s2 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 in 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 qualitative 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
Isotopes: There are known 25 isotopes of manganese ranging from Mn-44 to Mn-67 and Mn-69. The only stable isotope is Mn-55. The next most stable isotope is Mn-53 with a half-life of 3.74 x 106 years. Density (g/cc): 7.21
Manganese Physical Data
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 The most common oxidation states are 0, +2, +6 and +7
Lattice Structure: Cubic
Lattice Constant (Å): 8.890
CAS registry number: 7439-96-5
- Manganese dioxide is used to make clear glass. Normal silica glass is tinted green and the manganese oxides add a purple tint to the glass that cancels out the green. Because of this property, glassmakers called it 'glassmaker's soap'.
- Manganese is found in the enzymes necessary to metabolize fats and carbohydrates.
- Manganese is found in the bones, liver, kidneys, and pancreas.
- Manganese is important in the processes that form bones, clots blood, and regulates blood sugar.
- As important as manganese is to our health, the body does not store manganese.
- Manganese is the 12th most abundant element in the Earth's crust.
- Manganese has an abundance of 2 x 10-4 mg/L in sea water (parts per million).
- The permanganate ion (MnO4-) contains the +7 oxidation state of manganese.
- Manganese was found in a black mineral called 'magnes' from the ancient Greek kingdom of Magnesia. Magnes was actually two different minerals, magnetite and pyrolusite. The pyrolusite mineral (manganese dioxide) was called 'magnesia'.
- Manganese is used in steel production to fix the sulfur found in iron ores. It also strengthens steel and prevents oxidation.
References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange's Handbook of Chemistry (1952), CRC Handbook of Chemistry & Physics (18th Ed.) International Atomic Energy Agency ENSDF database (Oct 2010)