Quick Facts
| Property | Value |
|---|---|
| Symbol | Mn |
| Atomic Number | 25 |
| Atomic Mass | 54.938 u |
| Category | Transition Metal |
| Period | 4 |
| Group | 7 |
| Block | d |
| Electron Configuration | [Ar] 3d⁵ 4s² |
Physical Properties
| Property | Value |
|---|---|
| State at 20°C | Solid |
| Density | 7.21 g/cm³ |
| Melting Point | 1246°C (1519 K) |
| Boiling Point | 2061°C (2334 K) |
| Appearance | Silvery-gray metal |
Atomic Properties
| Property | Value |
|---|---|
| Electron Configuration | [Ar] 3d⁵ 4s² |
| Electronegativity | 1.55 (Pauling scale) |
| First Ionization Energy | 717.3 kJ/mol |
| Atomic Radius | 127 pm |
| Covalent Radius | 139 pm |
| Van der Waals Radius | 197 pm |
History and Discovery
Discovered by: Johan Gottlieb Gahn Year of Discovery: 1774 Location: Stockholm, Sweden
Etymology
The name "manganese" comes from "magnesia nigra" (black magnite), named after Magnesia in Greece. It shares etymological roots with magnesium and magnetite.
Discovery Story
Manganese compounds were used by ancient peoples for glassmaking. Carl Wilhelm Scheele identified it as a distinct element in 1774. Johan Gottlieb Gahn isolated metallic manganese the same year by heating pyrolusite (MnO₂) with charcoal.
Isotopes
| Isotope | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|
| ⁵⁵Mn | 100% | Stable | - |
| ⁵³Mn | Trace | 3.7 million years | EC |
Occurrence
Natural Abundance
Manganese is the 12th most abundant element in Earth's crust (about 950 ppm). It never occurs free in nature. Primary ore is pyrolusite (MnO₂). Major deposits are in South Africa, Australia, China, Gabon, and Brazil. Massive manganese nodules cover parts of the ocean floor.
Extraction and Production
- Reduction: Of oxide ores with carbon or aluminum
- Electrolysis: For high-purity metal
- Sources: Pyrolusite mining, ocean nodules (future potential)
- Global production: about 20 million tons annually
Applications and Uses
Steel Production
- Essential alloying element (removes sulfur and oxygen)
- Hadfield steel (high-manganese, wear-resistant)
- HSLA steels
- 90% of manganese goes to steel production
Batteries
- Alkaline batteries (manganese dioxide cathode)
- Lithium-ion batteries
- Dry cell batteries
Chemical Industry
- Potassium permanganate (oxidizer, disinfectant)
- Manganese dioxide for glass decolorizing
- Catalysts
Other Uses
- Aluminum alloys
- Pigments (manganese violet)
- Animal feed supplement
Biological Role
Manganese is an essential trace element for all living organisms. It is a cofactor for many enzymes.
In the Human Body
- About 12 mg in adult body
- Concentrated in bones, liver, kidneys
- Essential for bone formation
- Required for metabolism of amino acids and carbohydrates
- Daily requirement: 1.8-2.3 mg
Dietary Sources
Whole grains, nuts, legumes, leafy vegetables, tea, and pineapple are rich in manganese.
Safety and Hazards
Toxicity
Chronic manganese exposure causes manganism, a Parkinson's-like neurological condition. Welders and miners are at particular risk.
Handling Precautions
- Fine powder is flammable
- Manganese dust requires respiratory protection
- Follow occupational exposure limits
- Manganese fumes from welding are hazardous
Environmental Impact
Manganese is naturally abundant. Mining activities can contaminate water sources. Some areas have naturally high groundwater manganese.
Interesting Facts
- Ancient Egyptians and Romans used manganese compounds for glassmaking
- Manganese nodules on the ocean floor contain trillions of tons of manganese
- The purple color of amethyst comes from manganese
- Hadfield steel, invented in 1882, remains important for railway crossings and rock crushers
- Manganese is named similarly to magnesium but they are very different elements