Cobalt
Definition and meaning of Cobalt in chemistry.
![Cobalt element card: symbol Co, atomic number 27, atomic mass 58.933, electron configuration [Ar] 3d⁷ 4s², oxidation states +3 +2, Transition metal, group 9, period 4, solid at room temperature.](/assets/images/terms/cobalt-chemical-element.webp)
Cobalt is a hard, shiny, transition metal with the chemical symbol Co and atomic number 27. It behaves as a ferromagnetic material, meaning it is strongly attracted to magnets. You will mostly find this metal naturally mixed with other metal ores deep in the Earth's crust.
In more detail
Cobalt sits in group 9 of the periodic table and remains magnetic at very high temperatures. It only loses its magnetism above 1121 degrees Celsius, a point known as the Curie temperature. In nature, miners usually extract cobalt from the ground alongside copper and nickel minerals.
This process yields cobalt as a byproduct of mining these other metals. When it reacts, cobalt typically forms compounds in either the +2 or +3 oxidation states. Many cobalt salts show brilliant blue or pink colors depending on the amount of water bound to them.
This color-changing property makes them useful as moisture indicators in laboratory drying agents. Some students mistake cobalt compounds for organic dyes due to their deep, vibrant blue color. However, this color comes from the way the metal ions absorb light in chemical solutions.
Cobalt metal resists rust and maintains its physical strength under intense heat and mechanical stress. This durability makes it excellent for building superalloys used in jet engine turbines. Biologically, cobalt is an essential trace element that sits at the center of vitamin B12. Doctors also use the radioactive isotope cobalt-60 to target and destroy cancer cells.
Key facts
| Field | General Chemistry |
|---|---|
| Symbol | Co |
| Atomic number | 27 |
| Atomic mass | 58.933 u |
| Category | Transition-Metal |
| Melting point | 1495 °C |
| State at STP | Solid |
Cobalt is a key component in the cathodes of modern lithium-ion batteries. The cathode represents the positive electrode that receives electrons while the battery is discharging. Adding cobalt increases the energy density of the battery and keeps it stable during charging cycles. Without this metal, rechargeable batteries would overheat quickly and degrade after only a few uses.
Frequently asked questions
Why is cobalt used in permanent magnets?
Cobalt increases the magnetic strength of alloys and helps them maintain magnetism at very high temperatures. This property makes it ideal for building strong, heat-resistant magnets used in motors.
What is the biological significance of cobalt?
Cobalt forms the central atom of vitamin B12, which animals need to produce healthy red blood cells. A severe deficiency in this vitamin can lead to serious nerve damage in humans.
What is cobalt blue and how is it made?
Cobalt blue is a famous pigment created by mixing cobalt oxides with aluminum compounds at high heat. Artists have used this chemically stable blue pigment for centuries to color ceramics and glass.
Related terms
Sources & references
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