Cobalt is a chemical element with symbol Co and atomic number 27. Like nickel, cobalt in the Earth's crust is found only in chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal.
Three reasons Cobalt stands out
1
Used in magnets and rechargeable batteries.
2
Its name comes from the German word for goblin, as medieval miners blamed it for making their copper ore toxic.
3
Vitamin B12, which is essential for human health, has an atom of this element at its very centre.
Blue glass, red blood cells, powerful magnets
Cobalt compounds have colored ceramics blue for centuries, long before the metal was understood. Today cobalt appears in heat-resistant superalloys, rechargeable batteries, and strong magnets. Biology needs only traces—vitamin B12 contains a cobalt atom—while excessive exposure is harmful.
Recognizing Cobalt in Elementle
If Cobalt is the mystery element, guesses below atomic number 27 point up and guesses above it point down. Its symbol is Co: a green letter matches the same position in that symbol, while a yellow letter belongs in another position.
The family clue turns green for transition metal guesses. Compare Iron (Fe), number 26 and Nickel (Ni), number 28: they share the family clue, but their atomic numbers and symbols help you tell them apart.
Values are reference data, not a specification for every temperature, pressure, or allotrope. Unknown properties are left unavailable. Superheavy-element predictions remain uncertain.
The introduction and original editorial story are adapted from Wikipedia contributors via Periodic-Table-JSON. Element descriptions and their adaptations are available under CC BY-SA 3.0. Numerical attributes use the PubChem periodic-table dataset, retrieved September 22, 2026.