Editing Period 5 element (section)

===Rhodium===

{{main|Rhodium}}

'''Rhodium''' is a [[chemical element]] that is a rare, silvery-white, hard, and [[chemically inert]] [[transition metal]] and a member of the [[platinum group]]. It has the [[chemical symbol]] '''Rh''' and [[atomic number]] 45. It is composed of only one [[isotope]], <sup>103</sup>Rh. Naturally occurring rhodium is found as the free metal, alloyed with similar metals, and never as a chemical compound. It is one of the rarest [[precious metal]]s and one of the most costly ([[gold]] has since taken over the top spot of cost per ounce).

Rhodium is a so-called [[noble metal]], resistant to corrosion, found in platinum or nickel ores together with the other members of the [[platinum group]] metals. It was [[discovery of the chemical elements|discovered]] in 1803 by [[William Hyde Wollaston]] in one such ore, and named for the rose color of one of its chlorine compounds, produced after it reacted with the powerful acid mixture [[aqua regia]].

The element's major use (about 80% of world rhodium production) is as one of the [[catalyst]]s in the [[Catalytic converter#Three-way|three-way catalytic converters]] of automobiles. Because rhodium metal is inert against corrosion and most aggressive chemicals, and because of its rarity, rhodium is usually [[alloy]]ed with [[platinum]] or [[palladium]] and applied in high-temperature and corrosion-resistive coatings. [[White gold]] is often plated with a thin rhodium layer to improve its optical impression while [[sterling silver]] is often rhodium plated for tarnish resistance.

Rhodium detectors are used in [[Nuclear reactor technology|nuclear reactors]] to measure the [[Neutron detection|neutron flux level]].