Curium Element Facts

The chemical element curium is classed as an actinide metal. It was discovered in 1944 by Glenn T. Seaborg, Ralph A.James, and Albert Ghiorso.

The Berkeley Lab’s 60-inch cyclotron.
60-inch Berkeley Lab Cyclotron

The Berkeley Lab's 60-inch cyclotron, where atoms of curium were synthesized for the first time. Ernest Lawrence, the cyclotron's inventor, is on the right.


Data Zone

Classification: Curium is an actinide metal
Color: silvery-white
Atomic weight: (247), no stable isotopes
State: solid
Melting point: 1340 oC , 1613 K
Boiling point: 3100 oC , 3373 K
Electrons: 96
Protons: 96
Neutrons in most abundant isotope: 151
Electron shells: 2,8,18,32,25,9,2
Electron configuration: [Rn] 5f7 6d1 7s2
Density @ 20oC: 13.5 g/cm3
Show more, including: Heats, Energies, Oxidation, Reactions, Compounds, Radii, Conductivities
Atomic volume: 18.28 cm3/mol
Structure: fcc: face-centered cubic
Specific heat capacity
Heat of fusion
Heat of atomization
Heat of vaporization
1st ionization energy 581 kJ mol-1
2nd ionization energy
3rd ionization energy
Electron affinity
Minimum oxidation number 0
Min. common oxidation no. 0
Maximum oxidation number 4
Max. common oxidation no. 3
Electronegativity (Pauling Scale) 1.3
Polarizability volume 23 Å3
Reaction with air
Reaction with 15 M HNO3
Reaction with 6 M HCl
Reaction with 6 M NaOH
Oxide(s) CmO, Cm2O3, CmO2
Hydride(s) CmH2
Chloride(s) CmCl3
Atomic radius 174 pm
Ionic radius (1+ ion)
Ionic radius (2+ ion)
Ionic radius (3+ ion) 111 pm
Ionic radius (1- ion)
Ionic radius (2- ion)
Ionic radius (3- ion)
Thermal conductivity
Electrical conductivity
Freezing/Melting point: 1340 oC , 1613 K

The Alpha Particle X-Ray Spectrometer

The Alpha Particle X-Ray Spectrometer (APXS) used on the Mars Exploration Rovers. It uses small amounts of curium-244 to determine the concentrations of most major elements in rocks and soil.(Photo credit: NASA)

Discovery of Curium

Dr. Doug Stewart

Curium was the third synthetic transuranium element of the actinide series to be discovered.

It was discovered by Glenn T. Seaborg, Ralph A.James, and Albert Ghiorso in 1944.

Curium-242 (half-life 162.8 days) was produced by bombarding plutonium-239 with alpha particles in the Berkeley, California, 60-inch cyclotron. Each nuclear reaction produced a neutron in addition to an atom of curium-242. (1)

The element was chemically identified at the metallurgical laboratory at the University of Chicago.

The researchers at first referred to curium as ‘delirium’ owing to the difficulties they encountered trying to isolate it from another new element with which it was very closely associated, americium – or ‘pandemonium’ as it was first called.

Visible amounts of curium-242, in the form of curium hydroxide, were first isolated by Louis Werner and Isadore Perlman of the University of California in 1947. Curium-242 was produced by bombarding americium-241 with slow moving neutrons for a year. (2)

In 1952, W. W. Crane, J. C. Wallmann, and Burris B. Cunningham prepared metallic curium for the first time at Berkeley, California. (3)

The element is named after Marie and Pierre Curie, who pioneered work on radioactivity and discovered radium and polonium.

Transuranium elements discovery and experiments. 1963 chemistry educational documentary narrated by Glenn Seaborg, Stanley Thompson and Albert Ghiorso.

Appearance and Characteristics

Harmful effects:

Curium is harmful due to its radioactivity. It accumulates in bones and destroys the marrow, stopping the formation of red blood cells.


Curium is a hard, dense radioactive silvery-white metal.

It tarnishes slowly in dry air at room temperature.

Most compounds of trivalent curium are slightly yellow in color.

Curium is highly radioactive and it glows red in the dark. (4)

Uses of Curium

Curium is mainly used for scientific research purposes.

Curium-244 was used in the Alpha Proton X-ray Spectrometer (APXS) which measured the abundance of chemical elements in rocks and soils on Mars.

Curium-244 is a strong alpha emitter and is being studied as a potential power source in radioisotope thermoelectric generators (RTGs) for use in spacecraft and other remote applications.

Abundance and Isotopes

Abundance earth’s crust: nil

Abundance solar system: unknown

Cost, pure: $ per g

Cost, bulk: per 100g

Source: Curium does not exist in nature. It is a synthetic element and it is produced in nuclear reactors by bombarding plutonium with neutrons.

Isotopes: Curium has 15 isotopes whose half-lives are known, with mass numbers 238 to 252. Curium has no naturally occurring isotopes. Its longest lived isotopes are 247Cm, with a half-life of 15.6 million years, 248Cm with a half-life of 340,000 years and 250Cm with a half-life of 9,000 years.


1. Thomas K. Keenan, Americium and Curium., Journal of Chemical Education 36.1 (1959) p27.
2. J. C. Wallmann, The First Isolations of the Transuranium Elements., Journal of Chemical Education 36.7 (1959) p343.
3. Glenn Theodore Seaborg, The transuranium elements ., Taylor & Francis, 1958., page 93
4. Open Learn Labspace

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