All practice pages/Interatomic theory/Elements
Element 45, a transition metal
One of the rarest and most expensive precious metals, working mostly out of sight inside car exhaust systems.
Period 5, group 9. The other transition metals are tinted, and every cell opens its own article.
Rhodium has 45 electrons, one for every proton, so the atom carries no charge. Below are the same 45 electrons written two ways.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁸ 5s¹
Short form: [Kr] 4d⁸ 5s¹, where [Kr] stands for the 36 electrons krypton already has.
That list runs by shell. In the order the subshells fill it reads [Kr] 5s¹ 4d⁸, because a subshell fills by its energy, not by its shell number.
The simple form counts electrons shell by shell. The orbital form says which subshell each one sits in: s holds 2, p holds 6, d holds 10 and f holds 14. Shell 3 here is 3s² 3p⁶ 3d¹⁰, and 2 + 6 + 10 is 18.
Rhodium sits in period 5 and has 5 shells. The period number counts the shells.
The outer shell holds 1 electron. Those are the ones rhodium can lose, gain or share, so they are the ones that decide what it bonds with.
Like other transition metals, rhodium loses its outer s electrons, and often some d electrons as well, to form positive ions, and it can form more than one kind.
Among the rarest elements in the crust, found with platinum in South Africa, which mines most of it, and in Russia.
William Hyde Wollaston found it in 1803 in platinum ore from South America, shortly after he found palladium. He named it from the Greek rhodon, rose, for the pink color of its salts.
About 80% goes into catalytic converters, where it breaks down the nitrogen oxides in car exhaust. Rhodium also plates white gold jewelry for a bright finish, coats mirrors and reflectors, makes thermocouples for very hot furnaces, and catalyzes the production of several industrial chemicals.