Chromium is a mineral. It is called an “essential trace element” because very small amounts of chromium are necessary for human health. There are two forms of chromium.
Trivalent chromium is found in foods and supplements and is safe for humans. The other form, hexavalent chromium, is a known toxin that can cause skin problems and lung cancer. Only trivalent chromium is discussed here.
Chromium is used for chromium deficiency. It is also used for diabetes, high cholesterol, a hormonal disorder that causes enlarged ovaries with cysts (polycystic ovary syndrome or PCOS), and many other conditions, but there is no good scientific evidence to support most of these uses. But In this article, we discuss chromium as a metal and its properties and uses.
What Is Chromium Metal?
Chromium is a chemical element with the symbol Cr and the atomic number 24. It is the first element of group 6. It is a steel-gray, shiny, hard, and brittle transition metal. Chromium is the main additive in stainless steel, which gives anti-corrosive properties.
Chrome is also valued as a metal that can be polished to a mirror finish while resisting tarnishing. Polished chrome reflects almost 70% of the visible spectrum and almost 90% of the infrared light.
Chrome metal is valued for its high corrosion resistance and hardness. An important development in steel production was the discovery that steel can be made highly resistant to corrosion and discoloration by adding metallic chromium to form stainless steel. Stainless steel and chrome plating together make up 85% of commercial use.
The industrial production of chromium takes place from chromite ore (mostly FeCr2O4) to ferrochrome, an iron-chromium alloy, through aluminothermic or silicothermic reactions.
Ferrochrome is then used to make alloys such as stainless steel. Pure chrome metal is made by a different process: roasting and leaching chromite to separate it from iron, followed by reduction with carbon and then with aluminum.
|Group||6||Melting point||1907°C, 3465°F, 2180 K|
|Period||4||Boiling point||2671°C, 4840°F, 2944 K|
|Block||d||Density (g cm−3)||7.15|
|Atomic number||24||Relative atomic mass||51.996|
|State at 20°C||Solid||Key isotopes||52Cr|
|Electron configuration||[Ar] 3d54s1||CAS number||7440-47-3|
Who Discovered Chromium?
Chromium was discovered (1797) by the French chemist Nicolas-Louis Vauquelin and isolated as a metal a year later; it was named for its multicolored compounds. He produced chromium oxide (CrO3) by mixing crocoite with hydrochloric acid (HCl).
Although he believed a method for isolating chromium didn’t yet exist, Vauquelin was pleasantly surprised in 1798 to discover that he was able to obtain metallic chromium by simply heating chromium oxide in a charcoal oven.
Today, chromium is primarily obtained by heating the mineral chromite (FeCr2O4) in the presence of aluminum or silicon.
Properties of Chromium
Chromium is a lustrous, brittle, hard metal. Its color is silver-gray and it can be highly polished. It does not tarnish in the air, when heated it borns and forms green chromic oxide.
Chromium is unstable in oxygen, it immediately produces a thin oxide layer that is impermeable to oxygen and protects the metal below.
Chromium has a melting point of 1857+/-20°C, a boiling point of 2672°C, a specific gravity of 7.18 to 7.20 (20°C), with valences usually 2, 3, or 6. The metal is a lustrous steel-gray color that takes a high polish. It is hard and resistant to corrosion.
Chromium has a high melting point, stable crystalline structure, and moderate thermal expansion. All chromium compounds are colored. Chromium compounds are toxic.
Chromium metal is a chemical element by the symbol Cr and atomic number 24. It is the first element in group 6. Chromium is a fairly active metal. It does not react with water but reacts with most acids.
It combines with oxygen at room temperature to form chromium oxide (Cr2O3). Chromium oxide forms a thin layer on the metal surface, protecting it from further corrosion.
Chromium (Cr) is a brilliant, hard, refractory metal that melts at 1,857 °C (3,375 °F) and boils at 2,672 °C (4,842 °F). In its pure state, it is resistant to ordinary corrosion, resulting in its application as an electroplated protective coating for other metals. It dissolves in nonoxidizing mineral acids but not in aqua regia or nitric acid, which passivate the metal.
Because chromium and chromium-rich alloys are brittle at room temperature, they have limited application. By far the largest consumption is as an alloying addition to iron.
In amounts varying from 10 to 26 percent, chromium imparts corrosion resistance to steel; it is also used to improve hardenability, wear resistance, and high-temperature strength.
As the mineral chromite, chromium is employed extensively as a refractory material. Other chromium chemicals are used as pigments and tanning agents.
Uses of Chromium
A hard, silvery metal with a blue tinge. Chromium is used to harden steel, manufacture stainless steel (named as it won’t rust), and produce several alloys.
Chromium plating can be used to give a polished mirror finish to steel. Chromium-plated car and lorry parts, such as bumpers, were once very common. It is also possible to chromium plate plastics, which are often used in bathroom fittings.
About 90% of all leather is tanned using chrome. However, the waste effluent is toxic so alternatives are being investigated.
Chromium compounds are used as industrial catalysts and pigments (in bright green, yellow, red, and orange colors). Rubies get their red color from chromium, and glass treated with chromium has an emerald-green color.
Chromium Element and its uses
Chromium elements have many different uses. Some include:
- chromic fluoride (CrF 3): printing, dyeing, and mothproofing woolen cloth
- chromic oxide (Cr 2 O 3): a green pigment (coloring agent) in paint, asphalt roofing, and ceramic materials; refractory bricks; abrasive
- chromic sulfate (Cr 2 (SO 4) 3): a green pigment in paint, ceramics, glazes, varnishes, and inks; chrome plating
- chromium boride (CrB): refractory; a high-temperature electrical conductor
- chromium dioxide (CrO 2): covering for magnetic tapes (“chromium” tapes)
- chromium hexacarbonyl (Cr (CO) 6): catalyst; gasoline additive
As in Chromium, six electrons are current in the outermost shell, so Chromium has six valence electrons.
The electric configuration of chromium Cr is [Ar] 3d⁵ 4s¹.
Chromium is the first element in the sixth column of the periodic table. It is classified as a transition metal. Chromium atoms have 24 electrons and 24 protons with the most abundant isotope having 28 neutrons.
Chromium is used to harden steel, manufacture stainless steel, and produce several alloys. Chromium plating can be used to give a polished mirror finish to steel. Chromium-plated car and lorry parts, such as bumpers, were once very common.
Chromium is a hard steel-gray metal that takes a high polish and is used in alloys to increase strength and corrosion resistance.