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Manganese - Mn General Information Discovery Manganese was recognised as an element by Scheele, Bergman and others and isolated by J.G. Grahn in 1774 in Stockholm, Sweden. Appearance Manganese is a grey-white metal, resembling iron, but is harder and very brittle. Source Manganese minerals are widely distributed, pyrolusite and rhodochrosite being the most common. Manganese nodules have been found on the floor of the oceans. These nodules contain about 24% manganese together with smaller amounts of many other elements. Uses Manganese is used to form many important alloys. It gives steel a hard yet pliant quality, and with aluminium and antimony it forms highly ferromagnetic alloys. Manganese(IV) oxide is used as a depolariser in dry cells, and to decolorise glass coloured green by iron impurities. Manganese(II) oxide is a powerful oxidising agent and is used in quantitative analysis. Biological Role Manganese is an essential element. Without it, bones grow spongier and break more easily. It activates many enzymes and may be essential for utilization of vitamin B. Exposure to manganese dust, fumes and compounds is to be avoided as it is a suspected carcinogen. General Information Manganese is reactive chemically, and decomposes cold water slowly. It is reactive even when impure, and will burn in oxygen. |
| Physical Information | |||
| Atomic Number | 25 | ||
| Relative Atomic Mass (12C=12.000) | 54.938 | ||
| Melting Point/K | 1517 | ||
| Boiling Point/K | 2235 | ||
| Density/kg m-3 | 7440 (293K) | ||
| Ground State Electron Configuration | [Ar]3d54s2 | ||
| Electron Affinity(M-M-)/kJ mol-1 | +94 |
| Key Isotopes | ||||||
| nuclide | 53Mn | 54Mn | 55Mn | 56Mn | ||
| atomic mass | 52.941 | 53.940 | 54.938 | |||
| natural abundance | 0% | 0% | 100% | 0% | ||
| half-life | 2x106 yrs | 303 days | stable | 2.576 h |
| Other Information | ||
| Enthalpy of Fusion/kJ mol-1 | 14.4 | |
| Enthalpy of Vaporisation/kJ mol-1 | 220.5 | |
| Oxidation States | ||
| main | Mn+2 | |
| others | Mn-3, Mn-2, Mn-1, Mn0, Mn+1, | |
| Mn+3, Mn+4, Mn+5, Mn+6, Mn+7 | ||
| Ionisation Energies/kJ mol-1 | ||
| M - M+ | 717.4 | |
| M+ - M2+ | 1509.0 | |
| M2+ - M3+ | 3248.4 | |
| M3+ - M4+ | 4940 | |
| M4+ - M5+ | 6990 | |
| M5+ - M6+ | 9200 | |
| M6+ - M7+ | 11508 | |
| M7+ - M8+ | 18956 | |
| M8+ - M9+ | 21400 | |
| M9+ - M10+ | 23960 | |
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