Manganese

Manganese, ₂₅Mn
General properties
Pronunciation	/ˈmæŋɡəniːz/ (MANG-gə-neez)
Appearance	silvery metallic
Standard atomic weight (Ar, standard)	54.938044(3)
Manganese in the periodic table
	chromium ← manganese → iron
Atomic number (Z)	25
Group	group 7
Period	period 4
Element category	transition metal
Block	d-block
Electron configuration	[Ar] 3d5 4s2
Electrons per shell	2, 8, 13, 2
Physical properties
Phase at STP	solid
Melting point	1519 K (1246 °C, 2275 °F)
Boiling point	2334 K (2061 °C, 3742 °F)
Density (near r.t.)	7.21 g/cm3
when liquid (at m.p.)	5.95 g/cm3
Heat of fusion	12.91 kJ/mol
Heat of vaporization	221 kJ/mol
Molar heat capacity	26.32 J/(mol·K)
Atomic properties
Oxidation states	7, 6, 5, 4, 3, 2, 1, −1, −2, −3 acidic, basic or amphoteric; depending on the oxidation state
Electronegativity	Pauling scale: 1.55
Ionization energies	1st: 717.3 kJ/mol; 2nd: 1509.0 kJ/mol; 3rd: 3248 kJ/mol; (more);
Atomic radius	empirical: 127 pm
Covalent radius	Low spin: 139±5 pm; High spin: 161±8 pm
	Spectral lines
	Spectral lines
Miscellanea
Crystal structure	body-centered cubic (bcc)
Speed of sound thin rod	5150 m/s (at 20 °C)
Thermal expansion	21.7 µm/(m·K) (at 25 °C)
Thermal conductivity	7.81 W/(m·K)
Electrical resistivity	1.44 µΩ·m (at 20 °C)
Magnetic ordering	paramagnetic
Magnetic susceptibility	(α) +529.0·10−6 cm3/mol (293 K)
Young's modulus	198 GPa
Bulk modulus	120 GPa
Mohs hardness	6.0
Brinell hardness	196 MPa
CAS Number	7439-96-5
History
Discovery	Carl Wilhelm Scheele (1774)
First isolation	Johann Gottlieb Gahn (1774)
Main isotopes of manganese
β+	52Cr
γ	–
γ	–
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Manganese is a chemical element with symbol Mn and atomic number 25. It is not found as a free element in nature; it is often found in minerals in combination with iron. Manganese is a metal with important industrial metal alloy uses, particularly in stainless steels.

Historically, manganese is named for pyrolusite and other black minerals from the region of Magnesia in Greece, which also gave its name to magnesium and the iron ore magnetite. By the mid-18th century, Swedish-German chemist Carl Wilhelm Scheele had used pyrolusite to produce chlorine. Scheele and others were aware that pyrolusite (now known to be manganese dioxide) contained a new element, but they were unable to isolate it. Johan Gottlieb Gahn was the first to isolate an impure sample of manganese metal in 1774, which he did by reducing the dioxide with carbon.

Manganese phosphating is used for rust and corrosion prevention on steel. Ionized manganese is used industrially as pigments of various colors, which depend on the oxidation state of the ions. The permanganates of alkali and alkaline earth metals are powerful oxidizers. Manganese dioxide is used as the cathode (electron acceptor) material in zinc-carbon and alkaline batteries.

In biology, manganese(II) ions function as cofactors for a large variety of enzymes with many functions. Manganese enzymes are particularly essential in detoxification of superoxide free radicals in organisms that must deal with elemental oxygen. Manganese also functions in the oxygen-evolving complex of photosynthetic plants. While the element is a required trace mineral for all known living organisms, it also acts as a neurotoxin in larger amounts. Especially through inhalation, it can cause manganism, a condition in mammals leading to neurological damage that is sometimes irreversible.