Difference between revisions of "Manganese"
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===Physical=== | ===Physical=== | ||
| − | Manganese is a silvery-gray metal, which has similar properties to iron. It is hard and very brittle. It melts at 1246 °C and boils at 2061 °C. It has a density of 7.21 g/cm<sup>3</sup>, being slightly less dense than iron. | + | Manganese is a silvery-gray metal, which has similar properties to [[iron]]. It is hard and very brittle. It melts at 1246 °C and boils at 2061 °C. It has a density of 7.21 g/cm<sup>3</sup>, being slightly less dense than iron. |
==Availability== | ==Availability== | ||
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:3 MnO<sub>2</sub> + 4 Al → 3 Mn + 2 Al<sub>2</sub>O<sub>3</sub> | :3 MnO<sub>2</sub> + 4 Al → 3 Mn + 2 Al<sub>2</sub>O<sub>3</sub> | ||
| − | :MnO<sub>2</sub> + C → Mn + CO<sub>2</sub> | + | : MnO<sub>2</sub> + C → Mn + CO<sub>2</sub> |
The reaction with aluminium is exothermic enough to reach the boiling point of manganese. Manganese lumps is somewhat difficult to separate from the the resulting slag. A fluxing agent such as [[calcium fluoride]] should be added, which also acts as heat sink. | The reaction with aluminium is exothermic enough to reach the boiling point of manganese. Manganese lumps is somewhat difficult to separate from the the resulting slag. A fluxing agent such as [[calcium fluoride]] should be added, which also acts as heat sink. | ||
Revision as of 19:57, 9 September 2019
| General properties | |||||
|---|---|---|---|---|---|
| Name, symbol | Manganese, Mn | ||||
| Appearance | Silvery-gray solid | ||||
| Manganese in the periodic table | |||||
| |||||
| Atomic number | 25 | ||||
| Standard atomic weight (Ar) | 54.938044(3) | ||||
| Group, block | , d-block | ||||
| Period | period 4 | ||||
| Electron configuration | [Ar] 3d5 4s2 | ||||
per shell | 2, 8, 13, 2 | ||||
| Physical properties | |||||
| Silvery-gray | |||||
| Phase | 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 | 5.95 g/cm3 | ||||
| Heat of fusion | 12.91 kJ/mol | ||||
| Heat of | 221 kJ/mol | ||||
| Molar heat capacity | 26.32 J/(mol·K) | ||||
| pressure | |||||
| 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 | ||||
| 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 | ||||
| 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 Ω·m (at 20 °C) | ||||
| Magnetic ordering | Paramagnetic | ||||
| Young's modulus | 198 GPa | ||||
| Bulk modulus | 120 GPa | ||||
| Mohs hardness | 6 | ||||
| Brinell hardness | 196 MPa | ||||
| CAS Registry Number | 7439-96-5 | ||||
| History | |||||
| Discovery | Torbern Olof Bergman (1770) | ||||
| First isolation | Johann Gottlieb Gahn (1774) | ||||
Manganese is a chemical element with symbol Mn and atomic number 25. It is a transition metal, often used in various steels and more often in chemistry, due to its large number of oxidation states.
Contents
Properties
Chemical
Manganese slowly tarnishes in air or in water containing dissolved oxygen.
Manganese reacts with all halogens, and most strong acids.
Manganese has 10 oxidation states, though the most common ones are +2, +3, +4, +6, and +7. Manganese compounds in oxidation state +7 are strong oxidizers.
Physical
Manganese is a silvery-gray metal, which has similar properties to iron. It is hard and very brittle. It melts at 1246 °C and boils at 2061 °C. It has a density of 7.21 g/cm3, being slightly less dense than iron.
Availability
Manganese metal is sold by various chemical suppliers. Manganese samples can also be bought from eBay and Amazon.
Isolation
Manganese metal can be extracted from manganese dioxide, readily found in many zinc-carbon batteries. The oxide can be reduced in a thermite reaction with aluminium or even magnesium, although carbon can also be used.
- 3 MnO2 + 4 Al → 3 Mn + 2 Al2O3
- MnO2 + C → Mn + CO2
The reaction with aluminium is exothermic enough to reach the boiling point of manganese. Manganese lumps is somewhat difficult to separate from the the resulting slag. A fluxing agent such as calcium fluoride should be added, which also acts as heat sink.
Better results can be obtained by replacing manganese dioxide with manganese(II,III) oxide (Mn3O4).
Manganese can also be extracted from manganese steels (mangalloy) by dissolving it in an acid, separating the manganese salt and reducing it to manganese metal through various methods.
Projects
- Make manganese dioxide
- Make potassium permanganate
- Element collecting
Handling
Safety
Manganese is an essential trace element for all known living organisms, however in large quantities has neurotoxic effects. It can cause a poisoning syndrome in mammals, especially when inhaled, leading to severe if not irreversible neurological damage.
Storage
Bulk manganese metal can be stored in any container, away from any corrosive vapors. Powdered manganese should be kept in sealed containers.
Disposal
Manganese compounds should be converted to insoluble or less harmful compounds, such as manganese(II,III) oxide. These can be placed in the same container as Zn-MnO2 batteries, as companies that deal in battery disposal will work with manganese wastes from damaged or leaking batteries.
