Rhodium: what kind of metal is it, its qualities, properties, and features

Rhodium is a simple substance, a solid transition metal, meaning its available electron energy levels are occupied such that the d band has the smallest possible number of electrons, 10 per atom. It is silvery-white in color and belongs to the platinum group of noble metals.

Rhodium is a minor element in the eighth group of the fifth period of Mendeleev's table of chemical elements. This metal was discovered relatively recently, in 1803, by William Wollaston, in a mine while working with native platinum. Rhodium is a very rare and dispersed element; its abundance is quite high in ultramafic igneous rocks. It does not exist as a distinct earth mineral. Rhodium can be found in the gold sands of South America, as well as in platinum and nickel ores, which are found there as a single compound.

Properties of rhodium

Rhodium has very good properties for a metal with a wide range of applications. Among its physical properties, rhodium has a high reflectivity of visible electromagnetic radiation. This allows it to be used to make so-called "surface" mirrors. Rhodium's density is 12.41 g/cm³. Due to its high density, it has a high melting point of 2239 K and a boiling point of 4000 K.

In its chemical properties, the noble metal rhodium surpasses platinum by a large margin. Metallic rhodium dissolves in aqua regia upon boiling, in sufficiently heated concentrated sulfuric acid, and in a mixture of sulfuric acid and hydrogen peroxide. Rhodium is highly chemically stable. Its reaction with non-metals occurs at red heat. Slow oxidation of finely ground rhodium occurs at temperatures above 6000°C. Reaction with concentrated sulfuric acid occurs upon slow heating, and with a solution of hydrogen and sodium hypochlorite.

Rhodium metal, its properties, characteristics and composition

Rhodium metal serves as an excellent catalyst, for example in catalytic converters used in automobile exhaust systems. And a rhodium-platinum alloy is an excellent catalyst for producing nitric acid by oxidizing ammonia with air.

Rhodium is an excellent structural material, successfully used in glass production. Specifically, the platinum-rhodium alloy is used as a spinneret for glass filaments in liquid crystal displays. Metallic rhodium is used to produce mirrors subject to high temperatures for high-power laser systems. Crucibles made of platinum-rhodium alloys are used to grow certain precious stones and electro-optic crystals. Rhodium's high resistance to electrical erosion allows it to be used as a contact material (connectors, sliding contacts).

Rhodium plays a vital role in the nuclear industry, where it's used to make detectors used to measure neutron flux. Rhodium also looks beautiful in jewelry. Its cool white luster complements diamonds, cubic zirconia, and other stones. It also serves as a valuable alloying element, hardening alloys, reducing wear, and imparting a brilliant shine. Rhodium's importance is significant in many areas.