25MnManganese

Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy uses, particularly in stainless steels. It improves strength, workability, and resistance to wear. Manganese oxide is used as an oxidising agent; as a rubber additive; and in glass making, fertilisers, and ceramics. Manganese sulfate can be used as a fungicide.

Manganese is also an essential human dietary element, important in macronutrient metabolism, bone formation, and free radical defense systems. It is a critical component in dozens of proteins and enzymes. It is found mostly in the bones, but also the liver, kidneys, and brain. In the human brain, the manganese is bound to manganese metalloproteins, most notably glutamine synthetase in astrocytes.

Manganese was first isolated in 1774. It is familiar in the laboratory in the form of the deep violet salt potassium permanganate. It occurs at the active sites in some enzymes. Of particular interest is the use of a Mn-O cluster, the oxygen-evolving complex, in the production of oxygen by plants.

Atomic properties

Standard atomic weight	54.938 ±2·10^-6
Atomic mass	54.938 u

Atomic radii

Radius (empirical)	127 pm
Radius (calculated)	161 pm
Covalent radius	139 ±5 pm

Atomic shell

Electron configuration	Ar 3d⁵ 4s²
Ionization energy	(1^st) 7.4340379 eV (2^nd) 15.63999 eV (3^rd) 33.668 eV (4^th) 51.21 eV (5^th) 72.41 eV
Shell model	Electrons k-shell:2 l-shell:8 m-shell:13 n-shell:2

Physical properties

Phase	solid
Density	7.43 g·cm⁻³ (298.1 K)
Molar volume	7.35·10^-6 m³·mol⁻¹
Speed of sound	5,150 m·s⁻¹ (293.1 K)

Temperatures

Melting point	1,519 K
Boiling point	2,334 K
Liquid range	815 K

Enthalpies

Melting enthalpy	13.2 kJ·mol^-1
Enthalpy of vaporization	220 kJ·mol^-1
Binding energy	281 kJ·mol^-1

Heat and conductivity

Specific heat capacity	479.5 J·kg⁻¹·K⁻¹
Thermal conductivity	7.8 W·m^-1·K^-1
Expansion coefficient	2.17·10^-5 K^-1
Work function	4.1 eV

Hardnesses

Mohs hardness	6
Brinell hardness	196 NM·m^-2

Elastic properties

Young’s modulus	198 GPa
Bulk modulus	120 GPa

Electrical properties

Electrical conductivity	694,000 S·m^-1
Resistance	1.44·10^-6 Ωm

Magnetism

Magnetism	antiferromagnetic
Magnetic susceptibility	5.29·10^-4 cm³·mol⁻¹ (293 K)

Chemical properties

Basicity	strongly acidic
Oxidation state	1, 2, 3, 4, (5), 6, 7
Standard potential	-1.18 V (Mn²⁺ + 2e^- → Mn)

Electronegativity

Pauling scale	1.55
Sanderson scale	2.2
Allred-Rochow scale	1.6
Ghosh-Gupta scale	3.434 eV
Nagle scale	1.36
Pearson absolute negativity	3.72 eV

Other properties

Natural occurrence	primordial
Crystal structure	Body-centered cubic
Goldschmidt Classification	siderophile
Superconductor	without transition tempperature
Price/kg	1.82 USD