In the previous elements, the energetic cost of promoting an electron to the next higher energy level is too great to compensate for that released by lessening inter-electronic repulsion. This occurs because electrons in the same orbital repel each other due to their like charges. This occurs again later in the periodic table with other elements and their electron configurations, such as copper, niobium, and molybdenum. It is also the first element in the periodic table whose ground-state electron configuration violates the Aufbau principle. Physical properties Atomic Ĭhromium is the fourth transition metal found on the periodic table, and has an electron configuration of 3d 5 4s 1. 7.3.1 Approved and disapproved health claims.Ībandoned chromium production sites often require environmental cleanup. According to the European Chemicals Agency (ECHA), chromium trioxide that is used in industrial electroplating processes is a Substance of Very High Concern (SVHC). While chromium metal and Cr(III) ions are considered non-toxic, hexavalent chromium, Cr(VI), is toxic and carcinogenic. However, in 2014, the European Food Safety Authority, acting for the European Union, concluded that there was insufficient evidence for chromium to be recognized as essential. In the United States, trivalent chromium (Cr(III)) ion is considered an essential nutrient in humans for insulin, sugar, and lipid metabolism. Pure chromium metal is produced by a different process: roasting and leaching of chromite to separate it from iron, followed by reduction with carbon and then aluminium. Ferrochromium is then used to produce alloys such as stainless steel. Industrial production of chromium proceeds from chromite ore (mostly FeCr 2O 4) to produce ferrochromium, an iron-chromium alloy, by means of aluminothermic or silicothermic reactions. The name of the element is derived from the Greek word χρῶμα, chrōma, meaning color, because many chromium compounds are intensely colored. Polished chromium reflects almost 70% of the visible spectrum, and almost 90% of infrared light. Chromium is also highly valued as a metal that is able to be highly polished while resisting tarnishing. Stainless steel and chrome plating ( electroplating with chromium) together comprise 85% of the commercial use. A major development in steel production was the discovery that steel could be made highly resistant to corrosion and discoloration by adding metallic chromium to form stainless steel.
Ĭhromium metal is valued for its high corrosion resistance and hardness.
It is a steely-grey, lustrous, hard, and brittle transition metal. Chromium is a chemical element with the symbol Cr and atomic number 24.
0 kommentar(er)
