Chromium
Definition and meaning of Chromium in chemistry.
![Chromium element card: symbol Cr, atomic number 24, atomic mass 51.996, electron configuration [Ar] 3d⁵ 4s¹, oxidation states +6 +3, Transition metal, group 6, period 4, solid at room temperature.](/assets/images/terms/chromium-chemical-element.webp)
Chromium is a chemical element with the symbol Cr and the atomic number 24. It is a steely-gray, lustrous, hard, and brittle transition metal found on the periodic table. This beautiful metal takes a high polish and naturally resists tarnishing when exposed to air.
In more detail
Chromium is the first element located in group 6 of the standard periodic table. It is renowned globally for its highly exceptional and unique physical magnetic properties. It is the only elemental solid that exhibits antiferromagnetic ordering at standard room temperature.
Antiferromagnetism means the magnetic moments of its atoms align in a regular but opposing pattern. This opposing alignment effectively cancels out the overall magnetic field of the solid metal material. Mining companies primarily extract it commercially for industry from a natural mineral called chromite.
The element demonstrates a complex chemistry characterized by a very wide range of oxidation states. The +3 and +6 oxidation states are definitely the most stable and common forms observed. The +2 oxidation state is also frequently observed by chemists during various chemical reactions.
Hexavalent chromium compounds, like chromates (CrO4 2-) and dichromates (Cr2O7 2-), act as powerful chemical oxidizers. These specific hexavalent compounds are known to be highly toxic and dangerous human carcinogens. In contrast, trivalent chromium is considered an essential trace element in the human diet.
It plays a helpful role in human lipid and sugar metabolism inside the body. However, its exact biological mechanism remains a subject of ongoing research in the medical field.
Key facts
| Field | General Chemistry |
|---|---|
| Symbol | Cr |
| Atomic number | 24 |
| Atomic mass | 51.996 u |
| Category | Transition-Metal |
| State at room temperature | Solid |
| Melting point | 1907 degrees Celsius |
| Year discovered | 1797 |
Global manufacturers heavily use chromium in the industrial production of commercial stainless steel materials. Workers add at least 11 percent chromium by mass to the standard steel mixture. This crucial addition creates a protective oxide layer that successfully prevents the steel from rusting. Chromium compounds are also widely used as bright pigments to color paints and decorative glass.
Frequently asked questions
Why is chromium metal so frequently used in industrial electroplating and metal finishing?
Chromium is used in electroplating because it provides an extremely hard and beautiful surface finish. This shiny outer coating is highly resistant to both chemical corrosion and visible surface tarnishing. It also makes the underlying metal much easier to clean and maintain over many years.
What is the primary difference between trivalent and hexavalent forms of chromium?
Trivalent chromium is a stable, naturally occurring form that is generally considered safe and essential. Hexavalent chromium is a toxic, anthropogenic compound that is a scientifically proven human carcinogen. Anthropogenic simply means that the compound is generated primarily through human industrial activities and pollution.
Related terms
Sources & references
See our sources and editorial standards.