Periodic Table


Atomic number: 45
Atomic weight: 102.90550
Symbol: Rh
Group number: 9
Electronic configuration: [Kr].4d85s1


Rhodium metal is silvery white. Rhodium has a higher melting point and lower density than platinum. It has a high reflectance and is hard and durable. Upon heating it turns to the oxide when red and at higher temperatures turns back to the element. It is a major component of industrial catalytic systems such as the BP-Monsanto process.

General information

Discoveror: William Hyde Wollaston
Date discovered: 1803
Discovered at: England
Meaning of name: From the Greek word "rhodon" meaning "rose"

Physical data

Standard state: solid at 298 K
Colour: silvery white metallic
Density of solid at ambient temperature/kg m-3: 12450
Molar volume/cm3: 8.28

Radii /pm

Atomic: 173
Covalent (single bond):
Pauling radius for the ion [Rh]-: no data

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius160.4no data60.4no data


Both values are quoted on the Pauling scale.

Pauling: 2.28
Allred Rochow: 1.45

Crystal Structure

structure: ccp (cubic close-packed)

The following CrystalMaker image represents the solid state structure. For most elements, the most stable allotrope is illustrated. Try WebElements version 2 for interactive virtual reality and CHIME images.


Temperatures (/K)

melting point: 2237
boiling point: 3968

Enthalpies /kJ mol-1

fusion: 26.6
vaporization: 494

single bond enthalpies:
Rh-F Rh-Cl Rh-Br Rh-I Rh-Rh
no data no data no data no data 285.4

Ionization enthalpies /kJ mol-1

Number Enthalpy


This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance
103Rh102.905500 (4)100

Further Information

Copyright 1997 Mark Winter
Department of Chemistry at the University of Sheffield, Sheffield S3 7HF, England.

The current version of this document is at http://www.shef.ac.uk/~chem/web-elements-I/Rh.html