Chromium contributes to stainless steel, polished metal coatings, and vividly colored compounds. Small amounts also give rubies their red color. These uses connect alloy design, surface treatment, and optical behavior, while reminding us that chromium in a metal and chromium in a compound are different materials.
FROM ELEMENT TO APPLICATION
AN ELEMENT IN CONTEXT
How does chromium help stainless steel resist corrosion at its surface?
Chromium-containing steel alloy
FOLLOW THIS RELATIONSHIP
Provide chromium within steel
A stainless steel contains chromium as part of an iron-based alloy, making chromium available throughout the material rather than only in decorative plating.
Explore the model (optional)
CrFORM → INTERACTION → CONSEQUENCE
Follow the explanation in either direction. These are authored steps, not a physical clock.
Vauquelin investigated crocoite and recognized a previously unknown element in the late 1790s. Its compounds produced colors that inspired the name chromium. The work connected analysis with color chemistry, extending beyond one specimen to other materials. Identifying the element helped explain why minerals with different compositions could nevertheless share a chemically related source of color.
1797–1798
Element identified and isolated
Vauquelin's work on crocoite established chromium through analysis and preparation.
Late 1790s
Color chemistry connected
Vauquelin associated chromium with the green coloration of emeralds.
Chromium is obtained chiefly from chromite, where it occurs combined with oxygen and other metals. The is a mineral material, distinct from a polished chromium coating. Obtaining useful chromium therefore involves changing and separating chemical forms, not merely removing pieces of free metal from a rock.
Chromium is a hard, lustrous metal that can take a highly polished surface. Many chromium compounds are strongly colored, and some act as oxidizing agents. Their different chemical forms must be distinguished: a metallic coating, a mineral , and a dissolved chromium compound do not have interchangeable properties.
Each section links its supporting references. Descriptions and diagrams were authored for this atlas. Source checks completed. Source checks dated 2026-09-06.
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Family labels and the group-3 layout are teaching conventions. A table position does not establish an unknown bulk property. Electronic configurations refer to neutral atoms; ions and material environments require their own account.
Read each reference property together with its units, conditions and the reference information below.
Not yet recorded: electron affinity, second ionization energy, ground-state term symbol, van der waals radius, thermal conductivity, specific heat capacity, electrical resistivity, crystal structure, lattice parameter a, space group, abundance in seawater, abundance in the universe, annual production, supply-risk listing, hazard classification, biological role, cas registry number, pubchem cid, wikidata item. These families are declared and awaiting an ingestion run against the source each names; they are listed here rather than shown as empty rows.
Physical
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Phase at 20 °C
solid
293.15 K, 101.325 kPa
Melting point in K
2180 K
at standard pressure unless noted
Boiling point in K
2944 K
101.325 kPa
Density in g/cm³
7.15 g/cm³
solids and liquids at 293 K; gases at 273 K and 101.325 kPa
Atomic and electronic
Intended reference: Pauling electronegativity scale · Widely tabulated; original in The Nature of the Chemical Bond
Electronegativity in Pauling
1.66 Pauling
Pauling scale
First ionization energy in kJ/mol
652.9 kJ/mol
gas-phase neutral atom, ground state
Covalent radius in pm
139 pm
single-bond covalent radius
Common oxidation states
+2, +3, +6
states met in ordinary compounds; not exhaustive
Occurrence and identity
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Abundance in the crust in mg/kg
102 mg/kg
upper continental crust, mass fraction
Has stable isotopes
Yesderived
Discovery year in CE
1797 CEderived
WHERE IT SITS AMONG ITS NEIGHBORS
Electronegativity across period 4
Cr 1.66 Pauling · Chromium
Electronegativity across period 4. Exact values.
K
0.82
Ca
1
Sc
1.36
Ti
1.54
V
1.63
Cr
1.66
Mn
1.55
Fe
1.83
Co
1.88
Ni
1.91
Cu
1.9
Zn
1.65
Ga
1.81
Ge
2.01
As
2.18
Se
2.55
Br
2.96
Kr
3
Electronegativity down group 6
Cr 1.66 Pauling · Chromium
Electronegativity down group 6. Exact values.
Cr
1.66
Mo
2.16
W
2.36
The trend uses the same reference-property values as the periodic table. Elements with no recorded value are left out of the line rather than drawn at zero.
