Chromium is a chemical element in the Periodic Table marked with the atomic number of 24 and with the chemical symbol Cr. This chemical element belongs to period 4 elements and the Transition Metals category. Similar to the rest of the Transition Metal elements Chromium possesses various metallic properties. In the Periodic Table Chromium is preceded by Vanadium and is followed by Manganese.
Chromium is a hard and brittle Transition Metal with various colorful compounds. It is greatly valued due to its hardness, resistance to corrosion, tarnishing and discoloration. While some Chromium compounds are considered as moderately toxic, it is valuable for living organisms as it plays a role for humans in their insulin, lipid metabolism and sugar levels. Apart from that Chromium also finds application in metallurgy, dye and pigments, woodwork, catalysts, and some cleaning detergents. It is among the most common chemical elements found on Earth and is the 22nd most abundant of all elements in the Earth’s crust. It is also present in seawater, freshwater and the Earth’s biosphere. It is most abundant in chromite ores.
Physical Characteristics of Chromium
In terms of physical characteristics Chromium possesses various metallic properties. It is a hard and brittle chemical element. Chromium has a steel grey lustrous finish and is highly resistant to corrosion, discoloration and tarnishing. The chemical compounds of Chromium have a wide specter of various colors. It has a relatively low density and crystalizes in a typical body-centered cubic crystal structure. Chromium has an antiferromagnetic ordering at standard room temperature and becomes paramagnetic at temperatures above 38 C. It has high melting and boiling points at 2180 K and 2944 K in their respective order.
Chemical Properties of Chromium
Atomic Number – 24
Group – 6
Period – 4
Block – d
Electronic Configuration – 3d5 4s1
Relative Atomic Mass – 51.9961 (51.9961 g/mol)
Molecular Weight – 51.9961
Electronegativity – 1.66
Density (G CM-3) – 7.19 g/cm3 at room temperature; 6.3 g/cm3 in liquid state
Melting Point – 2180 K; 1907 °C; 3465 °F
Boiling Point – 2944 K; 2671 °C; 4840 °F
Atomic Radius – 128 pm
Isotopes – 4
Electronic Shell – 2, 8, 13, 1
Discovery of Chromium
The discovery of Chromium has been credited to a French pharmacist and chemist, named Louis Nicolas Vauquelin. In 1797 he obtained several samples of crocoite ore (lead chromate) and analyzed them. A year later he isolated metallic chromium from the samples and eventually discovered traces of the element in various gemstones like emeralds and rubies. It was named Chromium after the Greek word “chroma”, which means color – due to the fact that its compounds come in a large variety of intense colors.
Recognized by: Louis Nicolas Vauquelin (1798)
Known and discovered by: Louis Nicolas Vauquelin (1798)
Named by: Louis Nicolas Vauquelin (1798)
Uses and role of Chromium
Chromium has a vast variety of uses and applications not only commercially, but also for human beings and other living organisms on Earth. It has a significant biological role as it is important for the insulin, sugar levels, and lipid metabolism. It is also used in metallurgy, pigmentation, woodwork, and other industries.
One of the main uses of Chromium is for the manufacturing of stainless steel due to its resistance to corrosion, tarnishing and discoloring. Various metallic alloys take up more than 80% of the global usage of Chromium for chemical, foundry and refractory uses. It is used in super-alloys, gas turbines, jet engines, coating, dyes, pigmentation, woodwork, some cleaning detergents, tanning of fibers and leather. Chromium is also used in the manufacturing of magnetic taping for audio tapes and cassettes, as oxidizing agent, and also as metal polish.
Chromium on Earth
Chromium is among the most common chemical elements found on Earth. It is the 22nd most abundant of all elements in the Earth’s crust and is also present in the Earth’s biosphere, in freshwater and in seawater. It is composed mostly in chromite ores and in some gem stones such as rubies and emeralds.
It has been discovered that most Chromium compounds aren’t toxic to the human body and as such, it can be used as a product of dietary reference intake. However, it has also been discovered that the intake of Chromium does not play any beneficial role to healthy people.