Quick Facts
| Property | Value |
|---|---|
| Symbol | Co |
| Atomic Number | 27 |
| Atomic Mass | 58.933 u |
| Category | Transition Metal |
| Period | 4 |
| Group | 9 |
| Block | d |
| Electron Configuration | [Ar] 3d⁷ 4s² |
Physical Properties
| Property | Value |
|---|---|
| State at 20°C | Solid |
| Density | 8.90 g/cm³ |
| Melting Point | 1495°C (1768 K) |
| Boiling Point | 2927°C (3200 K) |
| Appearance | Hard, lustrous, bluish-gray metal |
Atomic Properties
| Property | Value |
|---|---|
| Electron Configuration | [Ar] 3d⁷ 4s² |
| Electronegativity | 1.88 (Pauling scale) |
| First Ionization Energy | 760.4 kJ/mol |
| Atomic Radius | 125 pm |
| Covalent Radius | 126 pm |
| Van der Waals Radius | 192 pm |
History and Discovery
Discovered by: Georg Brandt Year of Discovery: 1735 Location: Stockholm, Sweden
Etymology
The name "cobalt" comes from the German "kobold" meaning "goblin" or "evil spirit." Miners believed goblins had contaminated valuable silver ore with this troublesome material.
Discovery Story
Georg Brandt discovered cobalt around 1735 while analyzing blue-colored ores. He showed that the blue color in glass and ceramics came from cobalt, not bismuth as previously believed. This made cobalt the first metal discovered in modern times (not known in antiquity).
Isotopes
| Isotope | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|
| ⁵⁹Co | 100% | Stable | - |
| ⁶⁰Co | Synthetic | 5.27 years | β⁻, γ |
Occurrence
Natural Abundance
Cobalt comprises about 25 ppm of Earth's crust. It rarely occurs free in nature, usually found in nickel-bearing ores. Major sources are cobaltite (CoAsS) and linnaeite (Co₃S₄). The Democratic Republic of Congo produces over 60% of global cobalt.
Extraction and Production
- Byproduct: Primarily from copper and nickel mining
- Processing: Roasting and reduction of ores
- Sources: DRC, Russia, Australia, Canada
- Global production: about 140,000 tons annually
Applications and Uses
Battery Technology
- Lithium-ion batteries (cobalt oxide cathodes)
- Electric vehicle batteries
- Smartphone and laptop batteries
- Critical for energy storage
Alloys and Superalloys
- Jet engine turbine blades
- Cutting tools (cemented carbides)
- Wear-resistant alloys
- Magnetic alloys (Alnico)
Chemicals and Pigments
- Cobalt blue pigment (glass, ceramics, paints)
- Catalysts (petroleum refining)
- Drying agents for paints and inks
Medical Applications
- Cobalt-60 for radiation therapy
- Sterilization of medical equipment
- Vitamin B12 (cyanocobalamin)
Biological Role
Cobalt is essential for life as the central atom in vitamin B12 (cobalamin).
In the Human Body
- About 1 mg in adult body
- Essential component of vitamin B12
- Required for red blood cell formation
- Needed for neurological function
- Daily B12 requirement: 2.4 μg
Dietary Sources
Vitamin B12 (containing cobalt) is found in meat, fish, eggs, and dairy products. Plant sources require supplementation.
Safety and Hazards
Toxicity
Excess cobalt is toxic, causing "beer drinker's cardiomyopathy" when used as a foam stabilizer (1960s). Cobalt dust and fumes can cause respiratory problems.
Handling Precautions
- Cobalt dust can cause hard metal lung disease
- Radioactive Co-60 requires special handling
- Skin contact may cause dermatitis
- Use appropriate respiratory protection
Environmental Impact
Cobalt mining in DRC has raised environmental and human rights concerns. Battery recycling is increasingly important.
Interesting Facts
- Cobalt has been used to color glass blue for over 4,000 years
- Cobalt is the only element essential for humans that wasn't known to ancient civilizations
- The DRC holds about half of the world's cobalt reserves
- Cobalt-60 gamma rays are used for cancer treatment and food sterilization
- Electric vehicle growth has dramatically increased cobalt demand