Chromium

=__**Chromium-Cr**__=


 * Atomic Number: 24**
 * Atomic Weight:** 51.9961
 * Melting Point:** 2180 K (1907°C or 3465°F)
 * Boiling Point:** 2944 K (2671°C or 4840°F)
 * Density:** 7.15 grams per cubic centimeter
 * Phase at Room Temperature:** Solid
 * Element Classification:** Metal
 * Period Number:** 4 **Group Number:** 6
 * Estimated Crustal Abundance:** 1.02×102 milligrams per kilogram
 * Estimated Oceanic Abundance:** 3×10-4 milligrams per liter
 * Number of Stable Isotopes:** 3
 * Ionization Energy:** 6.767 eV
 * Oxidation States:** +6, +3, +2


 * First Energy Level:** 2
 * Second Energy Level:** 8
 * Third Energy Level:** 13
 * Fourth Energy Level:** 1

Isotopes

 * ** Isotope ** || ** Half Life ** ||
 * Cr-49 || 42.3 minutes ||
 * Cr-50 || Stable ||
 * Cr-51 || 27.7 days ||
 * Cr-52 || Stable ||
 * Cr-53 || Stable ||
 * Cr-54 || Stable ||

Facts:

 * Date of Discovery:** 1797
 * Discoverer:** Louis Vauquelin
 * Name Origin:** From the Greek word //chrôma// (__color__)
 * Uses:** Stainless steel
 * Obtained From:** Chromite

__Characteristics:__ Chromium is a transition metal, with a lustrous steely-grap color, and has a high melting point. It's symbol is Cr. Odorless and tasteless. It is needed as a trace mineral in the diet for sugar and fat metabolism. In high amounts, it causes a toxicity. Chromium has a unique magnetic characteristic, it is the only element solid that show antiferromagnetic ordering at room temp and will turn paramagnetic above 38 degrees Celsius.

__History:__ Chromium was discovered in 1797 by Louis-Nicholas Vauquelin, while he was experimenting with a material known as Siberian red lead, also known as the mineral crocoite (PbCrO4). It is of great interest because of its high corrosion resistance and hardness. They discovered that they could add chromium to steel making it resistant to discoloration and less corrosion, thus stainless steel.

Chromium is the 21st most abundant element in Earth's crust with an average concentration of 100 ppm. Chromium compounds are found in the environment, due to erosion of chromium-containing rocks and can be distributed by volcanic eruptions. The concentrations range in soil is between 1 and 3000 mg/kg, in sea water 5 to 800 µg/liter, and in rivers and lakes 26 µg/liter to 5.2 mg/liter. Chromium is mined as chromite (FeCr2O4) ore. About two-fifths of the chromite ores and concentrates in the world are produced in South Africa, while Kazakhstan, India, Russia, and Turkey are also substantial producers. Untapped chromite deposits are plentiful, but geographically concentrated in Kazakhstan and southern Africa. Although rare, deposits of native chromium exist. The Udachnaya Pipe in Russia produces samples of the native metal. This mine is a kimberlite pipe, __rich__ in diamonds, and the reducing environment helped produce both elemental chromium and diamond.
 * Occurances:**

Approximately 4.4 million metric tons of marketable chromite ore were produced in 2000, and converted into ~3.3 million tons of ferro-chrome with an approximate market value of 2.5 billion United States __dollars__. The largest producers of chromium ore have been South Africa (44%) India (18%), Kazakhstan (16%) Zimbabwe (5%), Finland (4%) Iran (4%) and Brazil (2%) with several other countries producing the rest of less than 10% of the world production. The two main products of chromium ore refining are ferrochromium and metallic chromium. For those products the ore smelter process differs considerably. For the production of ferrochromium, the chromite ore (FeCr2O4) is reduced in large scale in electric arc furnace or in smaller smelters with either aluminium or silicon in an aluminothermic reaction.
 * Production:**

Source: []

__Uses for Chromium__ Clinical studies suggest that chromium supplements may be helpful for the following conditions: Researchers have studied the effects of chromium supplements for type 2 diabetes for many years. While some clinical studies have found no benefit, other clinical studies have reported that chromium supplements may reduce blood sugar levels as well as the amount of insulin people with diabetes need. In one double-blind, placebo-controlled study, people with type 2 diabetes who took chromium picolinate had better HbA1c values -- used to measure long-term control of blood sugar levels -- than those who took placebo. The group taking chromium also had better fasting blood glucose levels, a measure of short-term control of blood sugar levels. Another double-blind, placebo-controlled study looked at a combination of chromium and biotin. Half the people in the study took chromium picolinate and biotin, and the other half took placebo. Those who took chromium and biotin had better fasting glucose levels as well as HbA1c values. One study found that women who have diabetes as a result of being pregnant improved their __blood sugar__ control when they took chromium. But not all studies agree, and if chromium does help reduce blood glucose, it' s not clear how big the benefit might be. More research is needed. Chromium is often advertised as a weight-loss aid and a way to improve lean muscle and reduce body fat. Studies have been mixed, with some finding that chromium may help people lose weight and build muscle, and others finding that it had no effect. If chromium does work for weight loss, it seems that the effects are small compared to those of exercise and a well-balanced diet. Chromium is popular with some body builders and can be found in some sports nutrition supplements. But there is not much evidence that chromium helps people gain strength or build muscle mass. Most studies have been negative. Animal studies suggest that chromium may help lower blood pressure. But so far it has not been tested in people, so researchers don' t know if it would work. Clinical studies about whether chromium can lower cholesterol have been mixed. Some suggest that chromium may lower LDL or bad cholesterol, including one study that combined chromium with grape seed extract. In another study, people who were taking beta-blockers found that taking chromium raised their HDL or good cholesterol levels. Sources: []
 * Diabetes**
 * Weight loss and obesity**
 * Strength training**
 * Heart health**
 * used to harden steel, to manufacture stainless steel, and to form alloys
 * used in plating to produce a hard, beautiful surface and to prevent corrosion.
 * used to give glass an emerald green colour. It is responsible for the green colour of emeralds and the red colour of rubies
 * wide use as a catalyst
 * dichromates such as K2Cr2O7 are oxidising agents and are used in quantitative analysis and also in tanning leather
 * lead chromate as chrome yellow is a pigment
 * compounds are used in the textile industry as mordants
 * used by the aircraft and other industries for anodising aluminium
 * the refractory industry uses chromite for forming bricks and shapes, as it has a high melting point, moderate thermal expansion, and stable crystalline structure
 * tanning leather

As chromium compounds were used in dyes and paints and the tanning of leather, these compounds are often found in soil and groundwater at abandoned industrial sites, now needing environmental cleanup and remediation per the treatment of brownfield land. Primer paint containing hexavalent chromium is still widely used for aerospace and automobile refinishing applications. In 2010, the Environmental Working Group studied the drinking water in 35 American cities. The study was the first nationwide analysis measuring the presence of the chemical in U.S. water systems. The study found measurable hexavalent chromium in the tap water of 31 of the cities sampled, with Norman, Oklahoma, at the top of list; 25 cities had levels that exceeded California's proposed limit. Note: Concentrations of Cr VI in US municipal drinking water supplies reported by EWG are within likely, natural background levels for the areas tested and not necessarily indicative of industrial pollution (CalEPA Fact Sheet), as asserted by EWG. This factor was not taken into consideration in their report.
 * Environmental Problems:**


 * Symbol:** Cr **Atomic Number:** 24 **Atomic Mass:** 51.9961 amu **Melting Point:** 1857.0 °C (2130.15 K, 3374.6 °F) **Boiling Point:** 2672.0 °C (2945.15 K, 4841.6 °F) **Number of Protons/Electrons:** 24 **Number of Neutrons:** 28 **Classification:** Transition Metal **Crystal Structure:** Cubic **Density @ 293 K:** 7.19 g/cm3 **Color:** gray

Atomic Structure

 * [[image:http://www.chemicalelements.com/bohr/b0023.gif width="276" height="275"]] ||  || **Number of Energy Levels:** 4
 * First Energy Level:** **Second Energy Level:** **Third Energy Level:** **Fourth Energy Level:** ||

Isotopes

 * ** Isotope ** || ** Half Life ** ||
 * Cr-49 || 42.3 minutes ||
 * Cr-50 || Stable ||
 * Cr-51 || 27.7 days ||
 * Cr-52 || Stable ||
 * Cr-53 || Stable ||
 * Cr-54 || Stable ||

Facts:

 * Date of Discovery:** 1797 **Discoverer:** Louis Vauquelin **Name Origin:** From the Greek word //chrôma// (color) **Uses:** Stainless steel **Obtained From:** Chromite