Reed Relays and
Electronics India Limited
Manufacturer of Reed Switches, Reed Sensors and Reed-based products
Reed Relays and Electronics India Limited Incorporated in 1971


Rhodium is a chemical element with the symbol Rh and atomic number 45. It a hard silvery-white metal of the transition series. Dues to its low contact resistance and resistance to corrosion, it is used as a contact material in the production of reed switches.

Rhodium (Wikipedia)

Rhodium,  45Rh
Rhodium powder pressed melted.jpg
General properties
Pronunciation/ˈrdiəm/ (ROH-dee-əm)
Appearancesilvery white metallic
Standard atomic weight (Ar, standard)102.90549(2)
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


Atomic number (Z)45
Groupgroup 9
Periodperiod 5
Element category  transition metal
Electron configuration[Kr] 4d8 5s1
Electrons per shell
2, 8, 18, 16, 1
Physical properties
Phase at STPsolid
Melting point2237 K ​(1964 °C, ​3567 °F)
Boiling point3968 K ​(3695 °C, ​6683 °F)
Density (near r.t.)12.41 g/cm3
when liquid (at m.p.)10.7 g/cm3
Heat of fusion26.59 kJ/mol
Heat of vaporization493 kJ/mol
Molar heat capacity24.98 J/(mol·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−3, −1, +1, +2, +3, +4, +5, +6 (an amphoteric oxide)
ElectronegativityPauling scale: 2.28
Ionization energies
  • 1st: 719.7 kJ/mol
  • 2nd: 1740 kJ/mol
  • 3rd: 2997 kJ/mol
Atomic radiusempirical: 134 pm
Covalent radius142±7 pm
Color lines in a spectral range
Spectral lines of rhodium
Other properties
Crystal structureface-centered cubic (fcc)
Face-centered cubic crystal structure for rhodium
Speed of sound thin rod4700 m/s (at 20 °C)
Thermal expansion8.2 µm/(m·K) (at 25 °C)
Thermal conductivity150 W/(m·K)
Electrical resistivity43.3 nΩ·m (at 0 °C)
Magnetic orderingparamagnetic
Magnetic susceptibility+111.0·10−6 cm3/mol (298 K)
Young's modulus380 GPa
Shear modulus150 GPa
Bulk modulus275 GPa
Poisson ratio0.26
Mohs hardness6.0
Vickers hardness1100–8000 MPa
Brinell hardness980–1350 MPa
CAS Number7440-16-6
Discovery and first isolationWilliam Hyde Wollaston (1804)
Main isotopes of rhodium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
99Rh syn 16.1 d ε 99Ru
101mRh syn 4.34 d ε 101Ru
IT 101Rh
101Rh syn 3.3 y ε 101Ru
102mRh syn 3.7 y ε 102Ru
102Rh syn 207 d ε 102Ru
β+ 102Ru
β 102Pd
103Rh 100% stable
105Rh syn 35.36 h β 105Pd
| references

Rhodium is a chemical element with symbol Rh and atomic number 45. It is a rare, silvery-white, hard, corrosion-resistant and chemically inert transition metal. It is a noble metal and a member of the platinum group. It has only one naturally occurring isotope, 103Rh. Naturally occurring rhodium is usually found as the free metal, alloyed 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 found in platinum or nickel ores together 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, produced after it reacted with the powerful acid mixture aqua regia.

The element's major use (approximately 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-resistive coatings. White gold is often plated with a thin rhodium layer to improve its appearance while sterling silver is often rhodium-plated for tarnish resistance.

Rhodium detectors are used in nuclear reactors to measure the neutron flux level.

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