Located in the central part of the periodic table, in block D, chromium is one of the elements known as transition and is represented as ‘Cr’ . In nature we can find it, almost exclusively, in the form of compounds, chromite being the most important mineral in its compound.
In its pure formation, chromium is obtained through the reduction of chromium oxide with aluminum, through electrolysis or through chromic iodide.
Chromium characteristics
This transition metal is usually hard and brittle, bright gray in color, and highly resistant to corrosion. Their oxidation states are usually variable, although at levels +4 and +5 it is rare to find them in chromium.
Its highest level of oxidation is +6 and the most stable are at levels +2 and +3.
Chromium is used primarily in metallurgy to kill corrosion and give its compounds a shiny shape. In addition, in alloys, stainless steel is usually the one that contains the most chromium with around 12%.
In chrome plating processes, chrome is also often used to anodize aluminum. In addition, its use and that of some of its oxides as catalysts , for example, in the synthesis of ammonia, is very common.
Physicochemical properties
These are the physicochemical characteristics of chromium:
- Atomic number: 24.
- Valencia: 2,3,4,5,6.
- Oxidation state: +3.
- Electronegativity: 1.6.
- Covalent radius (Å): 1.27.
- Ionic Radius (Å): 0.69.
- Atomic radius (Å): 1.27.
- Electron configuration: [Ar] 3d 5 4s 1.
- First ionization potential (eV) 6.80.
- Atomic mass (g / mol): 51.996.
- Density (g / ml): 7.19.
- Boiling point (° C): 2665.
- Melting point (° C): 1875.
Element history
In 1797, the French chemist, Louis Nicolas Vauquelin , discovered this compound that no one had ever identified or used. Due to its multiple colors attached to its own compounds, he called it chromium, which came from the old Latin ‘chroma’ (color).
Originally, and until chemists and specialists had the opportunity to experiment with the element, it was used mainly in painting and for sculpture elements. It was at the end of the 19th century when its use changed to be used as an additive in steels.
Already at the end of the 19th century, thanks to aluminothermy, a series of chemical reactions where aluminum is used as a reducing agent, chemists were able to obtain metallic chromium.
Currently this metallic chrome is used in metals to obtain maximum resistance and bright colors in their finishes.
