Structure
Not a diagram of dots on rings — a Monte-Carlo sample of the actual probability density |ψ|² for each occupied subshell. Drag to rotate. Blue and violet mark opposite signs of the wavefunction, which is what makes bonding possible.
Measured values
Every bar shows where cobalt sits among all 118 elements for that property.
Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.
Size, to scale
Radius 125 pm — that is 0.125 nm, so about 4000 million of them side by side would span a millimetre.
Thermal range
Cobalt is liquid over a 1432 K window, from 1768 K to 3200 K.
The story
Cobalt is the magnetic superhero powering the digital revolution. This lustrous, silver-gray transition metal is absolutely essential for rechargeable batteries, permanent magnets, and jet engines. Named after "kobold," mischievous underground spirits from German folklore, cobalt has gone from being a nuisance for medieval miners to one of the most strategically important elements in the modern world. Discovered in 1735 by Swedish chemist Georg Brandt, cobalt was the first metal discovered since ancient times. For centuries, miners knew about mysterious blue ores that were difficult to smelt and often contained arsenic, making them sick. They blamed these problems on underground spirits called kobolds, never realizing they were dealing with a completely new element that would eventually power smartphones and electric cars. What makes cobalt absolutely extraordinary is its unique combination of magnetic and chemical properties. It's one of only three ferromagnetic elements (along with iron and nickel) that can be permanently magnetized. This makes it essential for creating the world's strongest permanent magnets when alloyed with rare earth elements - magnets so powerful they can lift cars and are used in wind turbines and electric vehicle motors. But cobalt's most important modern role is in rechargeable batteries. Lithium cobalt oxide cathodes in lithium-ion batteries can store enormous amounts of energy while being charged and discharged thousands of times. Your smartphone, laptop, and electric car all depend on cobalt to store and release energy efficiently. As the world transitions to renewable energy and electric vehicles, demand for cobalt has skyrocketed. Here's something concerning: about 70% of the world's cobalt comes from the Democratic Republic of Congo, often from mines with poor working conditions. This has led to intensive research into cobalt-free battery technologies and ethical sourcing initiatives.
Georg Brandt (1694-1768), a Swedish chemist and mineralogist, discovered cobalt around 1735 while investigating blue-colored ores from copper mines near Sala, Sweden. Local miners called these troublesome ores "kobold" (German for goblin) because they contained no copper despite their appearance and produced toxic arsenic fumes when roasted.
Brandt's systematic analysis revealed that the blue color came from a previously unknown metal rather than bismuth or other known elements. His careful chemical procedures isolated cobalt compounds and demonstrated their distinct properties, establishing cobalt as the first metal discovered through scientific investigation rather than ancient metallurgical practices.
Commercial cobalt production began with cobalt blue pigment manufacturing in the 18th century, prized for its stability and intense color. Modern cobalt metallurgy developed during World War I when Germany's Krupp steelworks discovered cobalt's superalloy properties, leading to strategic military applications.
Applications
Cobalt transforms turbine engines from impossible dreams to aerospace reality through its exceptional high-temperature strength and corrosion resistance. This strategic metal enables jet engines, medical implants, and rechargeable batteries that power our modern technological world.
Cobalt-based superalloys maintain strength at temperatures exceeding 1000°C, enabling jet engine turbine blades and combustion chambers to operate under extreme conditions. Stellite alloys containing 50-65% cobalt provide exceptional wear resistance for cutting tools, valve seats, and industrial equipment. Gas turbine engines in commercial aircraft rely on cobalt superalloys for critical rotating components where failure could be catastrophic.
Lithium cobalt oxide (LiCoO₂) cathodes power most smartphones, laptops, and consumer electronics through cobalt's ability to reversibly intercalate lithium ions. Electric vehicle batteries increasingly use nickel-cobalt-manganese (NCM) and nickel-cobalt-aluminum (NCA) cathodes that balance energy density, safety, and cost while reducing cobalt content due to supply constraints.
Cobalt-chromium alloys create artificial hip and knee joints with exceptional biocompatibility and wear resistance. These implants last 20-30 years in the human body while maintaining structural integrity under constant mechanical stress. Dental applications utilize cobalt alloys for partial dentures and orthodontic appliances requiring strength and corrosion resistance.
Alnico magnets containing aluminum, nickel, and cobalt provide high-temperature magnetic stability for speakers, sensors, and industrial applications. Samarium-cobalt magnets operate reliably at temperatures up to 350°C, making them essential for aerospace and automotive applications where neodymium magnets would fail.
Where it comes from
25 mg/kg of Earth's crust · more abundant than 75% of elements
Cobalt forms through neutron capture processes in massive stars and during supernova nucleosynthesis events. The primary cobalt isotope, cobalt-59, represents the endpoint of iron peak nucleosynthesis, formed when nuclear binding energy reaches its maximum efficiency in stellar cores.
Earth's crust contains only 30 parts per million cobalt, making it relatively rare compared to other transition metals. Most terrestrial cobalt occurs as a byproduct in nickel and copper ores rather than forming independent cobalt minerals, contributing to supply chain concentration and geopolitical concerns.
Democratic Republic of Congo produces 70% of global cobalt from copper-cobalt sedimentary deposits in the Katanga Province. These deposits formed through weathering and oxidation of sulfide ores, creating cobalt-rich laterites and oxidized zones. Carrollite (CuCo₂S₄) and cobaltite (CoAsS) represent primary cobalt minerals, though most production comes from mixed sulfide ores.
Manganese nodules on deep ocean floors contain significant cobalt concentrations (0.2-0.3%), representing potential future resources as terrestrial supplies become constrained. These nodules form through extremely slow precipitation processes over millions of years in oxygen-rich deep waters.
Cobalt's strategic importance and supply concentration drive extensive recycling efforts. Battery recycling recovers cobalt from spent lithium-ion batteries, while superalloy recycling recycles cobalt from aerospace components, achieving recovery rates exceeding 95% in sophisticated facilities.
Handling
Cobalt compounds can cause serious health effects including hard metal lung disease and allergic contact dermatitis. Occupational exposure requires comprehensive safety measures due to cobalt's potential carcinogenicity and respiratory sensitization.
Cobalt dust inhalation causes pulmonary fibrosis and "hard metal lung disease" in workers exposed to cobalt-tungsten carbide dusts. Skin sensitization leads to cobalt allergies affecting 1-3% of the population, causing dermatitis from jewelry, clothing fasteners, and occupational exposure.
Respiratory protection, local exhaust ventilation, and skin protection prevent cobalt exposure. Medical surveillance including pulmonary function testing and allergy screening helps detect early health effects in exposed workers.
Quick answers
Cobalt (symbol Co) is element 27 on the periodic table, a transition metal in period 4, group 9. The blue in medieval stained glass and Ming porcelain, and half of the magnets that hold hard drives together. At room temperature it is a solid.
[Ar] 3d⁷ 4s², giving 4 occupied shells holding 2, 8, 15, 2 electrons respectively.Cobalt melts at 1768 K (1494.9 °C) and boils at 3200 K (2926.9 °C).
The standard atomic weight of Cobalt is 58.933 u. That is a weighted average across its naturally occurring isotopes, which is why it is rarely a whole number.
Cobalt has a density of 8.9 g/cm³. Water is 1.0 g/cm³, so a block of cobalt is about 8.9× heavier.
Cobalt has a Pauling electronegativity of 1.88. The scale runs from 0.70 (francium, the least greedy for electrons) to 3.98 (fluorine, the most). Values in this middle band tend to form covalent rather than strongly ionic bonds.
Cobalt was discovered in 1735 by Georg Brandt. It is named after german kobold, "goblin" — miners blamed it for bad ore.
Cobalt makes up about 25 mg/kg of the Earth's crust — uncommon, but not rare.