Manganese
[Ar] 3d⁵ 4s² · 2 · 8 · 13 · 2
The metal with the widest span of oxidation states in the table, from −3 to +7. Steel is impossible without it: manganese scavenges sulfur and oxygen, which otherwise leave the metal brittle.
3D model
Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.
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Atomic properties
- Atomic number
- 25
- Atomic mass
- 54.938 а.е.м.
- Electron configuration
- [Ar] 3d⁵ 4s²
- Electrons per shell
- 2 · 8 · 13 · 2
- Block
- d-block
- Group
- Manganese group
- Period
- 4
- Electronegativity (Pauling)
- 1.55
- Electronegativity (Allen)
- 1.75
- Atomic radius
- 161 pm
- Covalent radius
- 139 pm
- Van der Waals radius
- 197 pm
- Ionisation energy 1
- 717.3 kJ/mol
- Ionisation energy 2
- 1 509 kJ/mol
- Ionisation energy 3
- 3 248 kJ/mol
- Ionisation energy 4
- 4 940 kJ/mol
- Ionisation energy 5
- 6 990 kJ/mol
- Electron affinity
- 0 kJ/mol
- Common oxidation states
- +2, +4, +7
- Oxidation states
- -3, -2, -1, +1, +2, +3, +4, +5, +6, +7
Physical properties
- State at 25 °C
- solid
- Density
- 7.21 g/cm³
- Melting point
- 1 519 K · 1 245.9 °C
- Boiling point
- 2 334 K · 2 060.9 °C
- Speed of sound
- 5 150 m/s
Thermal properties
- Heat of fusion
- 12.91 kJ/mol
- Heat of vaporisation
- 221 kJ/mol
- Specific heat capacity
- 0.479 J/(g·K)
- Thermal conductivity
- 7.81 W/(m·K)
Mechanical properties
- Young's modulus
- 198 GPa
- Shear modulus
- 76 GPa
- Bulk modulus
- 120 GPa
- Poisson ratio
- 0.35
- Mohs hardness
- 6
- Brinell hardness
- 196 MPa
Electrical and magnetic properties
- Electrical resistivity
- 1 440 nΩ·m
- Magnetic ordering
- paramagnetic
- Curie point
- no data
- Néel point
- no data
- Superconducting point
- no data
Crystal structure
- Crystal structure
- complex cubic
- Lattice constants
- a = 891.25 pm
Abundance
- In the crust
- 950 mg/kg
- In the ocean
- 0.0002 mg/L
- In the universe
- 8 000 mg/kg
- In the human body
- 0.2 mg/kg
Isotopes
| Isotope | Abundance | Half-life | Decay mode |
|---|---|---|---|
| 53Mn | — | 3.7 Myr | ЭЗ |
| 55Mn | 100 % | stable | — |
Manganese-55 is the only stable isotope. Manganese-53, half-life 3.7 million years, is used in cosmochronology.
Discovery
- Year of discovery
- 1774
- Discovered by
- Johan Gottlieb Gahn
- Where
- Sweden
- Origin of the name
- from a corruption of magnesia, the mineral pyrolusite
History
Pyrolusite had decolourised glass since antiquity. Johan Gahn isolated the metal in 1774 on a hint from Scheele, who had shown that pyrolusite held a new element.
Where it occurs
950 mg/kg of the crust, the twelfth most abundant element. The main ores are pyrolusite and rhodochrosite, and ferromanganese nodules carpet parts of the ocean floor.
How it is produced
Carbon reduction of the oxides gives ferromanganese; electrolysis of the sulfate gives the pure metal. The largest producers are South Africa, Australia and Gabon.
Role in living things
An essential micronutrient: manganese sits in mitochondrial superoxide dismutase and in the enzyme that splits water during photosynthesis. That manganese cluster in photosystem II releases all the oxygen in the atmosphere.
Safety
Chronic inhalation of manganese dust causes manganism, a Parkinson-like neurological disorder documented in welders and miners.
Uses
- Steel: about 90 % of all manganese, as deoxidiser and alloying addition
- Hadfield steel with 12 % manganese work-hardens on impact — used for excavator teeth and rail crossings
- Cathode material in lithium-ion batteries
- Potassium permanganate as oxidiser and antiseptic
- Decolourising glass — the old glassmaker's soap
Curiosities
- The oxygen we breathe is released by a four-atom manganese cluster inside plant chloroplasts.
- Manganese spans more oxidation states than any other element.
- Potassium permanganate stains a solution intense violet and goes colourless on reduction — a classic titration endpoint.
- The cave paintings at Lascaux were made with manganese and iron oxides.