Cobalt Element Properties
Complete reference for Cobalt (Co, element 27): atomic data, electron configuration, oxidation states, physical constants, and chemical behavior.
Cobalt
Transition Metal — Period 4, Group 9
Atomic Identity
Electron Configuration
Three unpaired 3d electrons give cobalt a magnetic moment of ~1.7 μB per atom. Cobalt has the highest Curie temperature (1115 °C) of any ferromagnetic element.
Physical Properties
Chemical Properties
Oxidation States in Detail
| State | Key Compounds | Color | Notes |
|---|---|---|---|
| +3 | [Co(NH₃)₆]³⁺, Co₂O₃, CoF₃, Co(acac)₃ | Yellow / Green / Dark brown | Most stable in coordination complexes; key catalyst state |
| +2 | CoCl₂, CoO, CoSO₄, Co(H₂O)₆²⁺ | Pink / Blue / Red | Most stable free-ion state; cobalt chloride used as humidity indicator |
| +4 | CoO₂, BaCoO₃ | Dark | Strongly oxidizing; rare under normal conditions |
| +1 | Co(CO)₄⁻ derivatives | Varies | Organometallic; low-valent complexes with pi-acceptor ligands |
| 0 | Co₂(CO)₈, Co₄(CO)₁₂ | Orange / Black | Metal carbonyls; important industrial catalysts (hydroformylation) |
| −1 | Co(CO)₄⁻ (cobalt tetracarbonyl anion) | Colorless | Rare anionic organometallic; strong nucleophile |
Key Facts About Cobalt
Ferromagnetic Element
Cobalt is one of only three naturally ferromagnetic elements (iron and nickel are the others). Its Curie temperature of 1115 °C is the highest of any ferromagnet, making it essential for high-temperature permanent magnets.
Vitamin B12 Core
Cobalt is the central metal ion in vitamin B12 (cobalamin), the only vitamin containing a metallic element. It is coordinated in a corrin ring and is essential for red blood cell formation and neurological function in humans.
Battery Cathode Material
Lithium cobalt oxide (LiCoO₂) is the dominant cathode material in lithium-ion batteries used in smartphones and laptops. The Co³⁺/Co⁴⁺ redox couple enables reversible charge storage at ~3.9 V.
Cobalt Blue Pigment
Cobalt aluminate (CoAl₂O₄) produces the stable, vivid cobalt blue pigment used in ceramics, glass, and paints since the 8th century. The Co²⁺ ion in a tetrahedral oxygen field gives its characteristic blue color.
Superalloys
Cobalt-based superalloys (e.g., Stellite, Haynes 188) retain high strength and oxidation resistance above 1000 °C. They are critical for jet engine turbine blades, industrial gas turbines, and cutting tools.
Discovered 1735
Swedish chemist Georg Brandt isolated cobalt in 1735, making it the first metal discovered since antiquity. The name derives from the German "Kobold" (goblin), as miners blamed mysterious arsenic-containing cobalt ores for poisoning silver smelting.
Summary
Complete reference for Cobalt (Co, element 27): atomic data, electron configuration, oxidation states, physical constants, and chemical behavior.
How it works
- Browse the atomic identity section for symbol, atomic number, and standard atomic weight.
- Click the orbital diagram tabs to visualize the 3d and 4s electron arrangement interactively.
- Review the physical properties panel for density, melting point, boiling point, and magnetic behavior.
- Consult the chemical properties section for electronegativity, ionization energies, and oxidation states.
- Explore the oxidation states table to understand +2 and +3 cobalt chemistry and key compounds.
- Click any value to copy it to the clipboard for use in reports or calculations.
Use cases
- Look up cobalt constants for chemistry homework or exams.
- Verify atomic data when writing lab reports on transition metals.
- Reference electron configuration for d-block chemistry studies.
- Check physical properties for materials science and battery technology applications.
- Understand cobalt oxidation states for inorganic or coordination chemistry.
- Confirm magnetic properties for physics and materials engineering projects.
- Reference cobalt data for environmental and toxicology research.
- Teach or learn first-row transition metal chemistry using cobalt as an example.