Atomic / phase data
Reference values are evaluated.
BCC structure
Room-temperature chromium metal is BCC.
Species / safety
Cr metal, Cr(III) and hazardous Cr(VI) are kept distinct.
Geography
Chromite/ferrochrome commodity context is dated.
The lens describes evidence status, not confidence theatre. “Unknown” is kept unknown, and teaching schematics are not presented as direct measurements.
Chromium (Cr)
Chromium is element 24, a hard transition metal central to stainless steel and corrosion resistance. Its chemistry also teaches an essential safety distinction: metallic chromium, Cr(III) compounds and Cr(VI) compounds are not interchangeable.
Chromium atomic number, mass, electron configuration and key properties
Chromium: quick answers
How many protons, neutrons and electrons does chromium have?
Chromium’s atomic number is 24, so every chromium atom has 24 protons, and a neutral atom also has 24 electrons. Its most common natural isotope, chromium-52, has 28 neutrons (other isotopes have different neutron counts).
What is the symbol for chromium?
The chemical symbol for chromium is Cr.
Is chromium a solid, liquid or gas at room temperature?
Chromium is a solid at room temperature (about 25 °C).
What family (group) is chromium in?
Chromium is a transition metal, in group 6, period 4 of the periodic table.
What is the electron configuration of chromium?
The ground-state electron configuration of chromium is [Ar] 3d⁵ 4s¹.
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.
24 protons define chromium.
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.
Chromium in its period and family
Chromium is a Period 4 Group 6 transition metal. Its near-half-filled d shell supports multiple oxidation states and rich coordination chemistry.
Chromium Visual Lab
Rotate BCC chromium, inspect the half-filled 3d shell, switch among Cr metal / Cr(III) / Cr(VI) chemistry, and connect stainless steel, chromite supply, colored compounds and corrosion resistance.
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.
Chromium in one minute
Atomic number 24 means 24 protons.
Chromium’s ground state is [Ar] 3d⁵4s¹, an important electron-configuration exception.
Metallic chromium is BCC at ordinary conditions.
Chromium is essential to stainless steel and many corrosion-resistant alloys.
Cr(VI) compounds present serious health hazards; they must not be treated as equivalent to elemental Cr or Cr(III).
Shell rings organize electron counts. They are not electron trajectories or orbital shapes.
2 · 8 · 13 · 1 electrons
Atomic 3d/4s probability models explain electron occupancy, not the exact electronic band structure of chromium metal or the ligand-field states of chromium compounds.
Chromium is body-centred cubic near room temperature. The viewer is a conventional BCC cell; chromium compounds have entirely different structures.. 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
Atomic 3d/4s probability models explain electron occupancy, not the exact electronic band structure of chromium metal or the ligand-field states of chromium compounds.
Where do I meet chromium?
Clickable learning cards connect the element to materials, environment, technology, biology or research - depending on what the evidence actually supports.
Stainless steel
Chromium additions create corrosion-resistant stainless steels by enabling a protective chromium-rich oxide film.
Chromium metal vs Cr(III) vs Cr(VI)
Oxidation state changes chemistry, color, bonding and hazard; “chromium” is not one chemical species.
BCC transition metal
Metallic chromium contributes corrosion resistance and alloy performance.
Vanadium, chromium and manganese
Compare nearby elements to see which patterns repeat and which properties remain element-specific.
| Atomic no. | 23 |
|---|---|
| d count | 3d³ |
| Atomic no. | 24 |
|---|---|
| Ground state | 3d⁵4s¹ |
| Atomic no. | 25 |
|---|---|
| Ground state | 3d⁵4s² |
Chromium 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 | 24 | Source-reviewed; see Sources below | Evaluated |
| Relative atomic mass | 51.9961 | Source-reviewed; see Sources below | Evaluated |
| Ground-state electron configuration | [Ar] 3d⁵ 4s¹ | Source-reviewed; see Sources below | Evaluated |
| Group / period / block | Group 6 · Period 4 · d-block | Periodic-table placement | Evaluated |
| Electronegativity | 1.66 | Source-reviewed; see Sources below | Evaluated |
| Reference isotope | ⁵²Cr | Source-reviewed; see Sources below | Evaluated |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| State context | Hard silvery metal at 20 °C | Source-reviewed; see Sources below | Evaluated |
| Density | 7.15 g/cm³ | Source-reviewed; see Sources below | Evaluated |
| Material / molecular structure | Chromium metal · body-centred cubic | Chromium is body-centred cubic near room temperature. The viewer is a conventional BCC cell; chromium compounds have entirely different structures. | Measured |
| Classification | Transition metal | Periodic-table / chemistry classification | Evaluated |
| Structure-model scope | Chromium is body-centred cubic near room temperature. The viewer is a conventional BCC cell; chromium compounds have entirely different structures. | Teaching visualization; exact crystallographic coordinates are not implied unless stated. | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Melting / transition reference | 2180 K | Source-reviewed; see Sources below | Evaluated |
| Boiling / gas reference | 2944 K | Source-reviewed; see Sources below | Evaluated |
| Phase-path context | At approximately standard pressure, chromium remains BCC solid up to its melting region near 2180 K, then liquid to the boiling reference near 2944 K. This track does not attempt magnetic-order transitions or high-pressure polymorphs. | 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, +3, +6 (among several states) | Source-reviewed; see Sources below | Evaluated |
| Ion / common ion context | Cr³⁺ and Cr⁶⁺ compound contexts | Source-reviewed; see Sources below | Evaluated |
| Periodic chemistry context | Chromium is a Period 4 Group 6 transition metal. Its near-half-filled d shell supports multiple oxidation states and rich coordination chemistry. | Element-specific interpretation | Reviewed |
| Chemistry caution | Elemental form, ions and compounds are distinct chemical objects. | Interpretive teaching rule | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| ⁵²Cr | Stable · dominant natural isotope | Reference teaching nucleus: 24 protons and 28 neutrons. | Evaluated |
| ⁵³Cr | Stable natural isotope | Used in isotope-geochemistry applications including extinct-radionuclide systems. | Evaluated |
| ⁵⁰Cr and ⁵⁴Cr | Stable natural isotopes | Minor components of natural chromium. | Evaluated |
| Teaching nucleus | ⁵²Cr · 24 protons + 28 neutrons | Reference isotope used in the nucleus model | Reviewed |
Is Chromium a solid, liquid or gas? State at temperature
At approximately standard pressure, chromium remains BCC solid up to its melting region near 2180 K, then liquid to the boiling reference near 2944 K. This track does not attempt magnetic-order transitions or high-pressure polymorphs.
Where on Earth is Chromium found or produced?
Who discovered Chromium, and when?
Louis Nicolas Vauquelin identified chromium in crocoite and later isolated the metal.
Chromium pigments and plating became important industrial applications.
Stainless steel made chromium a core alloying element for corrosion-resistant infrastructure and products.
Chromium supply, stainless-steel recycling and control of hazardous Cr(VI) compounds are all important but distinct topics.
From chromite ore to chromium-bearing materials: a high-level path
Chromite ore is mined and concentrated in several countries; mine geography is distinct from ferrochrome and stainless-steel production.
Smelting converts suitable feed into ferrochromium for alloy production; operational furnace recipes are outside this educational page.
Stainless-steel and superalloy producers add chromium through ferroalloys, metal and recycled scrap.
Chromium chemicals follow separate conversion routes and require oxidation-state-specific handling and environmental controls.
What is chromium used for?
Stainless & heat-resistant steels
Chromium is a defining alloying element in stainless steel and many high-temperature alloys.
Surface engineering
Chromium-containing coatings/treatments are used for corrosion, appearance and wear performance.
Chemical compounds
Cr(III) and other chromium compounds are used in pigments, catalysts and specialty chemistry; specific species matter.
Recycling
Chromium in stainless-steel scrap can return to alloy production, reducing demand for primary units.
Chromium isotopes and natural abundance
⁵²Cr
Stable · dominant natural isotopeReference teaching nucleus: 24 protons and 28 neutrons.
⁵³Cr
Stable natural isotopeUsed in isotope-geochemistry applications including extinct-radionuclide systems.
⁵⁰Cr and ⁵⁴Cr
Stable natural isotopesMinor components of natural chromium.
Five-question Chromium check
Atomic number?
Ground-state configuration ending?
Room-temperature lattice?
Principal ore?
Which statement is scientifically correct?
Chromium 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 chromium’s atomic number?
Short answer: 24.
Atomic number is defined by proton count, so 24 protons are what make an atom chromium. A neutral chromium atom also has 24 electrons, while isotopes can have different neutron counts without changing the element.
Key point: Atomic number = proton count.
Is chromium a metal?
Short answer: Yes. Chromium is a transition metal.
This guide classifies Chromium as a transition metal. Its periodic position is Period 4, d-block, Group 6. Chromium is a Period 4 Group 6 transition metal. Its near-half-filled d shell supports multiple oxidation states and rich coordination chemistry.
Key point: Periodic-table classification describes recurring atomic/chemical behavior; it does not make every element in a column physically identical.
What is chromium used for?
Short answer: Its largest role is in stainless and alloy steels; it is also used in surface engineering and chemical compounds.
Stainless & heat-resistant steels: Chromium is a defining alloying element in stainless steel and many high-temperature alloys. Surface engineering: Chromium-containing coatings/treatments are used for corrosion, appearance and wear performance. “Chromium” is not one toxicological category. Oxidation state and chemical form matter enormously. Element Lookup separates Cr metal, Cr(III) and Cr(VI) rather than transferring properties from one form to another.
Key point: Always distinguish the pure element from the compound, alloy, isotope or device material that actually performs the application.
Why is chromium’s electron configuration unusual?
Short answer: The ground state is [Ar] 3d⁵4s¹ rather than a simple 3d⁴4s² pattern, reflecting the energetic balance of d and s subshells.
The neutral-atom ground-state reference used on this page is [Ar] 3d⁵ 4s¹. 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, +3, +6 (among several states), 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.
Is all chromium toxic in the same way?
Short answer: No. Chemical form and oxidation state matter. Cr(VI) compounds are a major health hazard and should not be equated with metallic chromium or Cr(III).
Hexavalent chromium compounds are serious occupational/environmental hazards. This page distinguishes oxidation states and does not provide recipes for producing or using hazardous Cr(VI) compounds.
Key point: Safety claims must be substance- and exposure-specific.
What ore supplies chromium?
Short answer: Chromite is the principal chromium ore mineral.
Chromite supply Chromium is obtained mainly from chromite ore and commonly enters steelmaking through ferrochromium. Chromium’s ground state is [Ar] 3d⁵4s¹, an important electron-configuration exception.
Key point: Use the direct answer together with the material, isotope and evidence context shown elsewhere on the page.
Scientific sources for Chromium
- Royal Society of Chemistry - Chromium
- NIST - Atomic Data for Chromium
- USGS - Mineral Commodity Summaries 2026
Questions to ask next about Chromium
A good element lesson should lead to the next useful question, not end after a list of facts.
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