Chromium

Chromium Details

Chromium Symbol: Cr

Chromium Atomic Number: 24

Chromium Atomic Weight: 51.996

What is Chromium?

Chromium (symbol Cr, atomic number 24) is the first element in Group 6 of elements. The other elements in this group are transition elements. They are molybdenum (Mo), tungsten (W), and seaborgium (Sg). Chromium is steely-gray in color, hard, and with a high melting point. It is without taste and odor. The name of this element comes from the Greek word "chroma", which actually means colour. This is because many of the compounds of this element have vibrant colors. The Chinese used this element to coat weapons as far back as two millenniums ago. In the late 18th century, this element was discovered in the mineral crocoite, which was used as a dye. In more recent times, chromium was also used to produce pigments.

This element is a very hard metal and hence highly resistant to rust. Chromium plays a major role in the development and production of stainless steel. The reason is that it makes steel highly resistant to corrosion and discoloration when it is mixed into it. Another popular application of the metal is in chrome plating.

Chromium is a relatively frequently found in the Earth's crust. At the same time, this element is not mined in pure form – it is mined as chromite. Around 40 percent of the chromite ores in the world are found in South Africa. The other deposits are in countries like Kazakhstan, India, and Russia as well as the Philippines, Zimbabwe, and Finland. Scientists estimate that the chromite deposits that have not been mined are far more than those which have. The reserves of chromium are estimated at one billion tones, with unexploited deposits found in Greenland. Deposits of pure chromium are very rare. There is one in Russia, which is rich in diamonds as well as chromium.

Among the isotopes of this element are 53Cr, 54Cr, and 52Cr, the last being the most abundant of the three. The half-life of one of the radioisotopes of chromium is extremely long – the most stable one, 50Cr, has a half-life of over 1.8×1017 years. On the other hand, the radioisotope 51Cr has a half-life of less than 28 days. The rest of the radioactive isotopes have even shorter half-lives - under 24 hours. Some even have half-lives that last several seconds.

Chromium is commonly used in metallurgy, dyes, plating, to preserve wood and tanning. Small amounts of the metal are found in high-speed tool steels, nickel-based alloys, jet engines, and gas turbines. It is the most commonly used metal coating because it is extremely durable. The element is used for chrome plating (on car and motorbike wheels) and decorative surfaces. A common pigment, used to color school buses among other things, is what is known as chrome yellow. This color does not photo degrade and is very strong. It was also used for the German postal service in the past.

In addition to these applications, the element is used in metallurgy, imparting a shiny finish and corrosion resistance. The salts of chromium color glass, and it is used in the production of synthetic rubies. Chromium is also used in the tanning of leather and dyeing as well as to produce molds for brick firing. Magnetic tape is produced with the use of chromium oxide.

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