Chromium (Cr)

By Sydney Reiff

Overall Description

Chromium is used in many things such as automobile trim and bathroom fittings because of its shiny finish and corrosion resistance.

Properties

Chromium has a high melting point of 1907ºC and a boiling point of 2671ºC. So it is most commonly found as a hard, silvery solid metal with a blue tinge. It has a density of 7.140 g/cc and an atomic radius of 166pm. Most metals are conductors and chromium follows that example while also being very brittle.


The element is used to harden steel and other metals so it has a very low reactivity. It is mostly only flammable as a powder.

History

Chromium was first discovered by a French Chemist named Nicholas Louis Vanquelin in Paris, 1798. Vanquelin was intrigued by a red mineral that was discovered in a gold mine (Siberian red lead) so he dissolved it in acid and precipitated the lead. Then he examined what was left and decided that he had isolated chromium. The Siberian red lead (crocoite) is a form of lead chromite.

Chromium Uses

Chromium is used to harden steel, to manufacture stainless steel and produce several alloys (a metal combining two or more metallic elements, especially to give greater strength). Then these steels are used to make bathroom fittings and car parts like bumpers.

Isotopes

Chromium has a few very useful isotopes. Cr-50 is used to produce radioisotope Cr-51 which is used to measure blood volume and red blood survival. Cr-53 and Cr-54 are used to study chromium metabolism and adult diabetes

Compounds

-lead chromate/chrome yellow: a yellow pigment in paint

-chromic oxide/chrome green: the 9th most abundant compound in the Earth’s crust, also used as a green pigment in paint

-potassium dichromate is used to tan leather

My Sources

- Element Card: Gray, Theodore W. (2008). The Photographic Card Deck of the Elements.

- Elements Book: Gray, Theodore W. (2009). The Elements: A visual exploration of every known atom in the universe. New York: Black Dog & Leventhal Publishers, Inc.

- Royal Society of Chemistry Periodic Table: http://www.rsc.org/periodic-table

- Los Alamos National Lab Periodic Table: http://periodic.lanl.gov/24.shtml

- Chromium Isotopes: http://www.tracesciences.com/cr.htm