Here are interesting facts about chromium, a transition metal with the element symbol Cr and atomic number 24. Chromium is known for being both an essential nutrient, yet toxic element and for its use in making chrome plating.
Interesting Chromium Facts
- Chromium is a member of the transition metal element group. It is the first element in group 6 of the periodic table.
- At ordinary temperature and pressures, chromium is a solid, steel-gray metal. It’s hard, lustrous, takes a high polish, resists corrosion, and has a high melting point.
- The name “chromium” comes from the Greek word chroma, which means color. This is because chromium compounds are intensely colorful. Chromium was first used as a red pigment from the mineral crocoite, which is lead(II) chromate. Louis Vauquelin purified the oxide in 1797 and was the first to isolate elemental chromium from crocoite in 1798, for which he gained credit for discovering the element. However, chromium compounds had been in use for thousands of years.
- Chromium is both an essential nutrient and a highly toxic metal, depending on its valence. Cr3+ is used in the body to metabolize sugars and lipids. Cr6+ or hexavalent chromium is extremely poisonous, causing brain damage and cancer and damaging numerous organ systems. While the 3+ and 6+ valences are most common, the +1, +4, and +5 oxidation states are also found. There’s also chromium(0), which is the metallic form of the element.
- Dietary sources of chromium(III) include meat, yeast, grains, produce, and supplements. Chromium(VI) is a water contaminant, plus it’s used to make steel, add color to glass green, to make chrome plating, and for industrial applications. About 85% of the use of chromium is for making metal alloys.
- The red color of rubies and the green color of emeralds is due to the presence of chromium. Like other transition metals, the different oxidation states are different colors, so chromium can be used to make a variety of pigments, including ones that are green, red, and yellow.
- The primary source of chromium is the mineral chromite. Chromium also (rarely) occurs in pure form in nature, sometimes in association with diamonds. Chromium is the 22nd most abundant element in the Earth’s crust, present at a concentration of about 100 parts per million.
- Chromium is the only solid chemical element that displays antiferromagnetic ordering at room temperature. It remains antiferromagnetic at cooler temperature, but changes to paramagnetic above 38 °C.
- Chromium is the element that makes stainless steel “stainless”. The exposed surface of chromium is passivated, forming a protective layer that protects the underlying metal from corrosion and discoloration.
- Natural chromium consists of three stable isotopes: Cr-52, Cr-54, and Cr-54. Chromium-52 is the most abundant isotope, accounting for 83.79% of the element. 19 radioactive isotopes are known, with the most stable being chromium-50. Chromium-50 has a half-life over over 1.8 x 1017 years.
Chromium Atomic Data
|Element Group||group 6, d-block|
|Electron Configuration||[Ar] 3d5 4s1|
|Melting Point||2180 K (1907 °C, 3465 °F)|
|Boiling Point||2944 K (2671 °C, 4840 °F)|
|Crystal Structure||body-centered cubic|