Rhodium

Rhodium is a chemical element; it has symbol Rh and atomic number 45. It is a very rare, dark silvery-white, hard, corrosion-resistant transition metal. It is a noble metal and a member of the platinum group. It has only one naturally occurring isotope, which is ¹⁰³Rh. Naturally occurring rhodium is usually found as a free metal or as an alloy with similar metals and rarely as a chemical compound in minerals such as bowieite and rhodplumsite. It is one of the rarest and most valuable precious metals. Rhodium is a group 9 element (cobalt group). It is used for the enhancement of jewelry.

Rhodium, ₄₅Rh

Rhodium
Pronunciation	/ˈroʊdiəm/ ⓘ ​(ROH-dee-əm)
Appearance	Silvery white metallic
Standard atomic weight Ar°(Rh)
	102.90549±0.00002 102.91±0.01 (abridged)
Rhodium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Co ↑ Rh ↓ Ir ruthenium ← rhodium → palladium
Atomic number (Z)	45
Group	group 9
Period	period 5
Block	d-block
Electron configuration	[Kr] 4d8 5s1
Electrons per shell	2, 8, 18, 16, 1
Physical properties
Phase at STP	solid
Melting point	2237 K ​(1964 °C, ​3567 °F)
Boiling point	3968 K ​(3695 °C, ​6683 °F)
Density (at 20° C)	12.423 g/cm3
when liquid (at m.p.)	10.7 g/cm3
Heat of fusion	26.59 kJ/mol
Heat of vaporization	493 kJ/mol
Molar heat capacity	24.98 J/(mol·K)
Specific heat capacity	242.736 J/(kg·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 2288 2496 2749 3063 3405 3997
Atomic properties
Oxidation states	common: +3 −3, −1, 0, +1, +2, +4, +5, +6, +7
Electronegativity	Pauling scale: 2.28
Ionization energies	1st: 719.7 kJ/mol 2nd: 1740 kJ/mol 3rd: 2997 kJ/mol
Atomic radius	empirical: 134 pm
Covalent radius	142±7 pm
Spectral lines of rhodium
Other properties
Natural occurrence	primordial
Crystal structure	​face-centered cubic (fcc) (cF4)
Lattice constant	a = 380.34 pm (at 20 °C)
Thermal expansion	8.46×10−6/K (at 20 °C)
Thermal conductivity	150 W/(m⋅K)
Electrical resistivity	43.3 nΩ⋅m (at 0 °C)
Magnetic ordering	paramagnetic
Molar magnetic susceptibility	+111.0×10−6 cm3/mol (298 K)
Young's modulus	380 GPa
Shear modulus	150 GPa
Bulk modulus	275 GPa
Speed of sound thin rod	4700 m/s (at 20 °C)
Poisson ratio	0.26
Mohs hardness	6.0
Vickers hardness	1100–8000 MPa
Brinell hardness	980–1350 MPa
CAS Number	7440-16-6
History
Naming	from Greek ῥόδον, 'rose', for the color of one of its chlorine compounds
Discovery and first isolation	William Hyde Wollaston (1804)
Isotopes of rhodium v e
Main isotopes Decay Isotope abun­dance half-life (t1/2) mode pro­duct 99Rh synth 16.1 d β+ 99Ru 100Rh synth 20.8 h β+ 100Ru 101Rh synth 4.07 y ε 101Ru 101mRh synth 4.343 d ε 101Ru IT 101Rh 102Rh synth 207 d β+ 102Ru β− 102Pd 102mRh synth 3.742 y β+ 102Ru IT 102Rh 103Rh 100% stable 105Rh synth 35.34 h β− 105Pd
Category: Rhodium view talk edit | references

Rhodium is found in platinum or nickel ores with the other members of the platinum group metals. It was discovered in 1803 by William Hyde Wollaston in one such ore, and named for the rose color of one of its chlorine compounds.

The element's major use (consuming about 80% of world rhodium production) is as one of the catalysts in the three-way catalytic converters in automobiles. Because rhodium metal is inert against corrosion and most aggressive chemicals, and because of its rarity, rhodium is usually alloyed with platinum or palladium and applied in high-temperature and corrosion-resistant coatings. White gold is often plated with a thin rhodium layer to improve its appearance, while sterling silver is often rhodium-plated to resist tarnishing.

Rhodium detectors are used in nuclear reactors to measure the neutron flux level. Other uses of rhodium include asymmetric hydrogenation used to form drug precursors and the processes for the production of acetic acid.