MANGANESE CHEMICAL & PHYSICAL PROPERTIES - 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. 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.

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Manganese Facts

Manganese Chemical & Physical Properties

by Anne Marie Helmenstine, Ph.D. 

Manganese Basic Facts

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 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 Trivia:

·      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 12^th 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)

Anne Marie Helmenstine, Ph.D.

Ph.D. in biomedical sciences from the University of Tennessee at Knoxville - Oak Ridge National Laboratory.

Science educator with experience teaching chemistry, biology, astronomy, and physics at the high school, college, and graduate levels.

ThoughtCo and About Education chemistry expert since 2001.

Widely-published graphic artist, responsible for printable periodic tables and other illustrations used in science.

Experience

Anne Helmenstine, Ph.D. has covered chemistry for ThoughtCo and About Education since 2001, and other sciences since 2013. She taught chemistry, biology, astronomy, and physics at the high school, college, and graduate levels. She has worked as a research scientist and also abstracting and indexing diverse scientific literature for the Department of Energy.

In addition to her work as a science writer, Dr. Helmenstine currently serves as a scientific consultant, specializing in problems requiring an interdisciplinary approach. Previously, she worked as a research scientist and college professor. 

Education

Dr. Helmenstine holds a Ph.D. in biomedical sciences from the University of Tennessee at Knoxville and a B.A. in physics and mathematics with a minor in chemistry from Hastings College. In her doctoral work, Dr. Helmenstine developed ultra-sensitive chemical detection and medical diagnostic tests.

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https://www.thoughtco.com/manganese-facts-606557