Chemical element chemical bonds, they form chemical compounds. Only a minority of elements are found uncombined as relatively pure minerals. Among the more common of such native elements are copper, silver, gold, carbon (as coal, graphite, or diamonds), and sulfur. All but a few of the most inert elements, such as noble gases and noble metals, are usually found on Earth in chemically combined form, as chemical compounds. While about 32 of the chemical elements occur on Earth in native uncombined forms, most of these occur as mixtures. For example, atmospheric air is primarily a mixture of nitrogen, oxygen, and argon, and
Cobalt boride Cobalt boride nanoparticless in the size range of 18 to 22 nm have also been produced. When used as a catalyst, cobalt boride is prepared by reducing a cobalt salt, such as Cobalt(II) nitrate, with sodium borohydride. Prior to reduction, the surface area of the catalyst is maximized by supporting the salt on another material; often this material is activated carbon. Cobalt boride Cobalt borides are inorganic compounds with the general formula CoB. The two main cobalt borides CoB and CoB. These are refractory materials. Cobalt boride is known to be exceptionally resistant to oxidation, a chemical property which makes