Periodic Table


Atomic number: 96
Atomic weight: 247
Symbol: Cm
Group number: (actinide)
Electronic configuration: [Rn].5f7.6d1.7s2


Most compounds of Cm(III) are faintly yellow. If curium enters the body it accumulates in the bones, and is therefore very toxic as its radiation destroys the red-cell forming mechanism. Curium is a radioactive rare earth metal. The most stable isotope is 247Cm which has a half-life of 16 million years. Curium is probably present in uranium ores. It has a few specialised uses but only a few of its compounds are known.

General information

Discoveror: Glenn T. Seaborg, Ralph A. James, Albert Ghiorso
Date discovered: 1944
Discovered at: USA
Meaning of name: Named after Pierre and Marie "Curie"

Physical data

Standard state: solid at 298 K
Colour: silver
Density of solid at ambient temperature/kg m-3: 13510
Molar volume/cm3: 18.05

Radii /pm

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

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius216.1no data113.146.3


Both values are quoted on the Pauling scale.

Pauling: 1.3
Allred Rochow: 1.2

Crystal Structure

structure: hcp (hexagonal 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: 1613
boiling point: 3383

Enthalpies /kJ mol-1

fusion: no data
vaporization: no data

single bond enthalpies:
Cm-F Cm-Cl Cm-Br Cm-I Cm-Cm
no data no data no data no data no data

Ionization enthalpies /kJ mol-1

Number Enthalpy


This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance

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/Cm.html