Atomic / phase data
Reference values are evaluated.
HCP / FCC allotropy
Both structures are measured; ~700 K is a teaching transition reference.
Battery context
Elemental metal is distinguished from cobalt-containing compounds.
Geography
Mine/refining geography is source-reviewed and dated.
The lens describes evidence status, not confidence theatre. “Unknown” is kept unknown, and teaching schematics are not presented as direct measurements.
Cobalt (Co)
Cobalt is element 27, a ferromagnetic transition metal used in high-performance alloys, magnets, catalysts and many battery materials. It also undergoes an HCP-to-FCC solid-state transition before melting.
Cobalt atomic number, mass, electron configuration and key properties
Cobalt: quick answers
How many protons, neutrons and electrons does cobalt have?
Cobalt’s atomic number is 27, so every cobalt atom has 27 protons, and a neutral atom also has 27 electrons. Its most common natural isotope, cobalt-59, has 32 neutrons (other isotopes have different neutron counts).
What is the symbol for cobalt?
The chemical symbol for cobalt is Co.
Is cobalt a solid, liquid or gas at room temperature?
Cobalt is a solid at room temperature (about 25 °C).
What family (group) is cobalt in?
Cobalt is a transition metal, in group 9, period 4 of the periodic table.
What is the electron configuration of cobalt?
The ground-state electron configuration of cobalt is [Ar] 3d⁷ 4s².
From atomic number to chemistry
Read these as a chain of causes, not as isolated facts. Each step links to the concept hub if you want the underlying idea explained.
27 protons define cobalt.
The ground-state configuration provides the starting point for its chemistry.
Periodic position organizes recurring chemistry and trends.
The teaching nucleus is one isotope, not the relative atomic mass.
Phase boundaries are condition-dependent and evidence-labelled.
Cobalt in its period and family
Cobalt is a Period 4 transition metal in Group 9, between iron and nickel. Its d electrons support magnetism and multiple oxidation states.
Cobalt Visual Lab
Inspect 3d orbitals, switch HCP↔FCC cobalt, compare metal with Co²⁺/Co³⁺ compound contexts, and explore magnets, superalloys, catalysts, batteries, mining and recycling.
Every mark points to one exact feature
The numbered markers explain the same information system used throughout Element Lookup. Unknown or predicted fields remain visibly labelled rather than being replaced with guesses.
Cobalt in one minute
Atomic number 27 means 27 protons.
Neutral cobalt has [Ar] 3d⁷4s².
⁵⁹Co is the only stable natural isotope.
Cobalt is ferromagnetic at room temperature.
Cobalt changes from HCP to FCC on heating before it melts.
Shell rings organize electron counts. They are not electron trajectories or orbital shapes.
2 · 8 · 15 · 2 electrons
The atomic 3d/4s clouds are isolated-atom probability models. Ferromagnetism and conductivity are collective solid-state effects and are not literal orbital animations.
Cobalt is HCP at ordinary temperature and transforms to an FCC form on heating at roughly 700 K. Both viewers are idealized teaching cells.. The viewer is evidence-aware: measured structures are identified as such; unknown bulk structures stay unknown.
Teaching visualization; not a literal finite sample or thermal trajectory.What this model does—and does not—show
The atomic 3d/4s clouds are isolated-atom probability models. Ferromagnetism and conductivity are collective solid-state effects and are not literal orbital animations.
Where do I meet cobalt?
Clickable learning cards connect the element to materials, environment, technology, biology or research - depending on what the evidence actually supports.
Superalloys
Cobalt-based and cobalt-containing superalloys retain useful properties in demanding high-temperature environments.
HCP ↔ FCC cobalt + ferromagnetism
Cobalt changes crystal structure before melting while its d electrons also support strong magnetic behavior.
Lower-temperature cobalt
Near room temperature cobalt is hexagonal close-packed.
Iron, cobalt and nickel
Compare nearby elements to see which patterns repeat and which properties remain element-specific.
| Atomic no. | 26 |
|---|---|
| Magnetic | Ferromagnetic |
| Atomic no. | 27 |
|---|---|
| Magnetic | Ferromagnetic |
| Atomic no. | 28 |
|---|---|
| Magnetic | Ferromagnetic |
Cobalt properties: atomic, physical, thermal and chemical
Categories follow the science of this element rather than a fixed decorative template. Each row carries condition/provenance context and an evidence label; unknown values stay unknown.
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Atomic number | 27 | Source-reviewed; see Sources below | Evaluated |
| Relative atomic mass | 58.933194 | Source-reviewed; see Sources below | Evaluated |
| Ground-state electron configuration | [Ar] 3d⁷ 4s² | Source-reviewed; see Sources below | Evaluated |
| Group / period / block | Group 9 · Period 4 · d-block | Periodic-table placement | Evaluated |
| Electronegativity | 1.88 | Source-reviewed; see Sources below | Evaluated |
| Reference isotope | ⁵⁹Co | Source-reviewed; see Sources below | Evaluated |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| State context | Hard grey ferromagnetic solid at 20 °C | Source-reviewed; see Sources below | Evaluated |
| Density | 8.86 g/cm³ | Source-reviewed; see Sources below | Evaluated |
| Material / molecular structure | Cobalt metal · HCP at lower temperature, FCC at higher temperature | Cobalt is HCP at ordinary temperature and transforms to an FCC form on heating at roughly 700 K. Both viewers are idealized teaching cells. | Measured |
| Classification | Transition metal | Periodic-table / chemistry classification | Evaluated |
| Structure-model scope | Cobalt is HCP at ordinary temperature and transforms to an FCC form on heating at roughly 700 K. Both viewers are idealized teaching cells. | Teaching visualization; exact crystallographic coordinates are not implied unless stated. | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Melting / transition reference | 1768 K | Source-reviewed; see Sources below | Evaluated |
| Boiling / gas reference | 3200 K | Source-reviewed; see Sources below | Evaluated |
| Phase-path context | The teaching path shows HCP cobalt at lower temperature, an HCP→FCC solid transition around 700 K, melting near 1768 K and boiling near 3200 K. The solid-transition temperature can depend on sample history and conditions. | Shared phase registry drives the slider, regions and markers. | Evaluated |
| Condition warning | Temperature and pressure define phase behavior; purity/allotropy may matter. | Teaching condition statement | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Ordinary electrical behavior | Metallic conductor | Qualitative bulk behavior; exact resistivity depends on temperature, purity and alloy state. | Measured |
| Conduction model | Collective solid-state electrons | Do not interpret isolated-atom orbital clouds as literal current paths. | Reviewed |
| Surface / compound caveat | Oxides, salts and alloys can behave differently from the pure metal | Material context | Reviewed |
| Engineering values | Condition-dependent | Use condition-specific materials data for engineering calculations. | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Common oxidation states | +2 and +3 | Source-reviewed; see Sources below | Evaluated |
| Ion / common ion context | Co²⁺ / Co³⁺ compound contexts | Source-reviewed; see Sources below | Evaluated |
| Periodic chemistry context | Cobalt is a Period 4 transition metal in Group 9, between iron and nickel. Its d electrons support magnetism and multiple oxidation states. | Element-specific interpretation | Reviewed |
| Chemistry caution | Elemental form, ions and compounds are distinct chemical objects. | Interpretive teaching rule | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| ⁵⁹Co | Stable · essentially all natural cobalt | Reference teaching nucleus: 27 protons and 32 neutrons. | Evaluated |
| ⁶⁰Co | Radioactive · important gamma source | Used in controlled industrial/medical contexts and as a tracer; it requires radiation-safety management. | Evaluated |
| Cobalt isotope context | One stable natural isotope | Natural cobalt is effectively monoisotopic, although many radioactive isotopes are known. | Evaluated |
| Teaching nucleus | ⁵⁹Co · 27 protons + 32 neutrons | Reference isotope used in the nucleus model | Reviewed |
Is Cobalt a solid, liquid or gas? State at temperature
The teaching path shows HCP cobalt at lower temperature, an HCP→FCC solid transition around 700 K, melting near 1768 K and boiling near 3200 K. The solid-transition temperature can depend on sample history and conditions.
Where on Earth is Cobalt found or produced?
Who discovered Cobalt, and when?
Georg Brandt identified cobalt as a distinct metal, helping separate its chemistry from bismuth and other ores.
Cobalt pigments, magnets and alloys expanded industrial use.
Cobalt-bearing superalloys became important in high-temperature turbine applications.
Battery demand, concentrated mine supply and recycling have made cobalt an important critical-mineral topic.
From cobalt-bearing ore to metal, alloy or compound: high-level context
Cobalt is commonly recovered as a coproduct or byproduct from copper and nickel ores rather than from a single universal “cobalt ore.”
Mining and beneficiation feed hydrometallurgical or pyrometallurgical industrial circuits; detailed process recipes are outside this guide.
Refining produces cobalt metal or chemical compounds to application-specific specifications.
Alloys, catalysts, magnets and battery materials use different cobalt forms, while recycling can recover cobalt from end-of-life products.
What is cobalt used for?
Superalloys
Cobalt helps selected alloys retain strength and corrosion resistance at high temperatures.
Permanent magnets
Cobalt-containing magnet families support high-temperature and high-performance applications.
Battery materials
Cobalt-containing cathodes are used in several lithium-ion battery chemistries.
Catalysts & pigments
Cobalt compounds are used in selected catalysts, drying agents, pigments and ceramics.
Cobalt isotopes and natural abundance
⁵⁹Co
Stable · essentially all natural cobaltReference teaching nucleus: 27 protons and 32 neutrons.
⁶⁰Co
Radioactive · important gamma sourceUsed in controlled industrial/medical contexts and as a tracer; it requires radiation-safety management.
Cobalt isotope context
One stable natural isotopeNatural cobalt is effectively monoisotopic, although many radioactive isotopes are known.
Five-question Cobalt check
Atomic number?
Stable natural isotope?
Room-temperature structure?
Higher-temperature solid structure?
Battery cobalt is usually present as…
Cobalt questions students commonly ask
Each answer starts with the direct fact, then explains the chemistry, evidence or material context so the result is understandable rather than merely memorized.
What is cobalt’s atomic number?
Short answer: 27.
Atomic number is defined by proton count, so 27 protons are what make an atom cobalt. A neutral cobalt atom also has 27 electrons, while isotopes can have different neutron counts without changing the element.
Key point: Atomic number = proton count.
Is cobalt a metal?
Short answer: Yes. It is a transition metal and is ferromagnetic at room temperature.
This guide classifies Cobalt as a transition metal. Its periodic position is Period 4, d-block, Group 9. Cobalt is a Period 4 transition metal in Group 9, between iron and nickel. Its d electrons support magnetism and multiple oxidation states.
Key point: Periodic-table classification describes recurring atomic/chemical behavior; it does not make every element in a column physically identical.
What is cobalt metal used for?
Short answer: Important uses include superalloys, magnets and specialty materials; cobalt compounds also appear in batteries, catalysts and pigments.
Superalloys: Cobalt helps selected alloys retain strength and corrosion resistance at high temperatures. Permanent magnets: Cobalt-containing magnet families support high-temperature and high-performance applications. Cobalt metal, cobalt ions and cobalt-containing battery compounds are different materials. A battery cathode containing cobalt is not a block of elemental cobalt, and supply geography is not chemistry.
Key point: Always distinguish the pure element from the compound, alloy, isotope or device material that actually performs the application.
How many valence electrons does cobalt have?
Short answer: Transition-metal valence counting depends on context; the neutral ground state is [Ar] 3d⁷4s².
The neutral-atom ground-state reference used on this page is [Ar] 3d⁷ 4s². This is an isolated-atom reference: bonding and ion formation can change which outer electrons are present or chemically active. The listed common oxidation-state context is +2 and +3, which helps connect the atomic configuration to ordinary chemistry without treating electron counting as a single universal rule.
Key point: Electron configuration is a ground-state atomic reference, not a literal picture of every compound.
Does cobalt change crystal structure when heated?
Short answer: Yes. Cobalt has a lower-temperature HCP form and a higher-temperature FCC form before melting.
Cobalt is HCP at ordinary temperature and transforms to an FCC form on heating at roughly 700 K. Both viewers are idealized teaching cells. The Structure viewer is an evidence-aware teaching model: measured or defensible structures are shown as models, while genuinely unknown bulk structures remain explicitly unknown.
Key point: A teaching lattice is a scientific model, not a photograph of a finite chunk of material.
Is cobalt in a battery elemental cobalt?
Short answer: Usually no. It is present in engineered compounds such as cathode materials.
Cobalt metal, cobalt ions and cobalt-containing battery compounds are different materials. A battery cathode containing cobalt is not a block of elemental cobalt, and supply geography is not chemistry. Battery materials Cobalt-containing cathodes are used in several lithium-ion battery chemistries.
Key point: The pure element, its ions, compounds and alloys are different materials and should not be treated as interchangeable.
Scientific sources for Cobalt
- Royal Society of Chemistry - Cobalt
- NIST - Atomic Data for Cobalt
- USGS - Mineral Commodity Summaries 2026
Questions to ask next about Cobalt
A good element lesson should lead to the next useful question, not end after a list of facts.
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