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Cobalt

physical science Maturity 13-18 Next article →

Cobalt is a chemical element with the symbol Co and atomic number 27. It is a hard, lustrous, and somewhat brittle gray metal.

Kobalt 13g
Kobalt 13g

In nature, cobalt is rarely found as a pure metal. Instead, it usually exists in the Earth's crust in a chemically combined form. It can sometimes be found in small amounts within alloys of natural meteoric iron. Cobalt is a ferromagnetic metal, which means it can be magnetized. It also has a specific gravity of 8.9. This element is essential to modern technology, biology, and industry.

Cobalt tool tip - 02
Cobalt tool tip - 02

The chemical properties of cobalt allow it to act in many different ways. It is a weakly reducing metal. This means it is protected from oxidation by a thin, passivating oxide film. However, it can be attacked by halogens and sulfur. When heated in oxygen, it produces cobalt(IV) oxide, known as Co3O4. This substance can lose oxygen at high temperatures to become cobalt monoxide, or CoO. Cobalt also reacts with several other elements. It reacts with fluorine at 520 K to create cobalt(III) fluoride. It also reacts with chlorine, bromine, and iodine to produce binary halides. Interestingly, it does not react with hydrogen or nitrogen gas, even when those gases are heated.

Cobalt exists in several different chemical forms and oxidation states. Common oxidation states for cobalt include +2 and +3. Many simple compounds use the +2 state, known as cobalt(II). These salts often form a pink-colored metal aquo complex when they are in water. If you add chloride to this solution, it turns into an intense blue color. Cobalt also forms various oxides. Cobalt(II) oxide is green and has a rocksalt structure. At temperatures between 600 and 700 °C, it oxidizes into the blue cobalt(II,III) oxide. Cobalt can also form complex coordination compounds. The chemist Alfred Werner won a Nobel Prize for his extensive work on these complex structures.

Cobalt(II)-chloride-hexahydrate-sample
Cobalt(II)-chloride-hexahydrate-sample

History shows that humans have interacted with cobalt for thousands of years. Since antiquity, cobalt-based blue pigments have been used for paints and jewelry.

Early blue and white ware circa 1335 Jingdezhen
Early blue and white ware circa 1335 Jingdezhen

These pigments also provide a distinctive blue tint to glass.

Cobalt blue flask
Cobalt blue flask

For a long time, people mistakenly believed the blue color came from the metal bismuth. The name "cobalt" itself has a mysterious history tied to 16th-century German silver miners. They called certain ores "kobold ore," which means "goblin ore" in German. Miners believed these ores were caused by mischievous spirits or gnomes. These ores were a nuisance because they were poor in useful metals. They also released poisonous, arsenic-containing fumes when they were smelted. In 1735, scientists discovered that these ores could be reduced to a new metal. This was the first new metal discovered since ancient times.

Today, cobalt production is a massive global industry. It is mostly produced as a by-product of mining for copper and nickel. It can also be extracted from metallic-lustered ores like cobaltite. The Copperbelt region, located in the Democratic Republic of the Congo (DRC) and Zambia, produces most of the world's cobalt.

Artisanal cobalt miners in the Democratic Republic of Congo
Artisanal cobalt miners in the Democratic Republic of Congo

In 2016, the DRC alone accounted for more than 50% of global production. By 2024, total world production exceeded 300,000 tons. During that same year, the DRC accounted for more than 80% of the total supply.

cobalt production, World, 2024 (cropped)
cobalt production, World, 2024 (cropped)

Cobalt has many vital uses in our modern world. It is a primary component in lithium-ion batteries. It is also used to manufacture high-strength, wear-resistant, and magnetic alloys.

Cobalt tool tip - 02
Cobalt tool tip - 02

In the petroleum industry, cobalt acts as a catalyst. It is used to refine crude oil by purging it of sulfur. Removing sulfur is important because sulfur is a major pollutant that causes acid rain when burned. Cobalt is also used in the form of radioisotopes. Cobalt-60 is a commercially important radioisotope. It is used as a radioactive tracer and to produce high-energy gamma rays.

Beyond machines and industry, cobalt is essential for life. It is the active center of a group of coenzymes called cobalamins. The most famous example is Vitamin B12, which is an essential vitamin for all animals.

Cobalt(II)-chloride-hexahydrate-sample
Cobalt(II)-chloride-hexahydrate-sample

Even in its inorganic form, cobalt serves as a micronutrient for fungi, algae, and bacteria. This shows how a heavy metal can be deeply connected to the biological systems of living things. From the tiny cells of a bacterium to the massive batteries in electric vehicles, cobalt plays a central role in our planet's systems.

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🖼️ Images & Media (12)
File:Kobalt 13g.jpg
Kobalt 13g.jpg
File:Cobalt tool tip - 02.jpg
Cobalt tool tip - 02.jpg
File:Cobalt(II)-chloride-hexahydrate-sample.jpg
Cobalt(II)-chloride-hexahydrate-sample.jpg
File:Tetrakis(1-norbornyl)cobalt(IV).png
Tetrakis(1-norbornyl)cobalt(IV).png
File:Early blue and white ware circa 1335 Jingdezhen.jpg
Early blue and white ware circa 1335...
File:cobalt production, World, 2024 (cropped).svg
cobalt production, World, 2024 (cropped).svg
File:Cobalt OreUSGOV.jpg
Cobalt OreUSGOV.jpg
File:Cobalt - world production trend.svg
Cobalt - world production trend.svg
File:World- Cobalt Production, 1944* - DPLA - c1037ee27d2f7452509d5cade20dc8b9.jpg
World- Cobalt Production, 1944* - DPLA -...
File:Artisanal cobalt miners in the Democratic Republic of Congo.jpg
Artisanal cobalt miners in the Democratic...
File:bristol.blue.glass.arp.750pix.jpg
bristol.blue.glass.arp.750pix.jpg
File:Cobalt blue flask.jpg
Cobalt blue flask.jpg
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