Curium (Cm)
Curium (symbol Cm) is the chemical element with atomic number 96: an actinide, solid at 0 °C, radioactive, made artificially, with an atomic mass of 247 u. Discovered in 1944 (Glenn T. Seaborg et al.).
Curium is a synthetic metal named in honor of Pierre and Marie Curie. Highly radioactive, it gives off a great deal of heat. Curium-244 equips the spectrometers of several Mars rovers, which bombard rocks with particles to work out their composition. Its most stable isotope, curium-247, has a half-life of 15.6 million years.
Key facts
- Atomic number
- 96
- Symbol
- Cm
- French name
- Curium
- Atomic mass
- 247 u
- Molar mass
- [247] g/mol
- Family
- Actinides
- Position
- period 7, f-block
- State at 0 °C
- Solid
- Melting point
- 1,339.9 °C
- Boiling point
- 3,109.9 °C
- Density
- 13.51 g/cm³
- Electronegativity (Pauling)
- 1.28
- First ionization energy
- 581 kJ/mol
- Atomic radius
- 176 pm
- Electron configuration
- [Rn] 5f⁷ 6d¹ 7s²
- Indicative price
- 190 million $/kg (order of magnitude)
- Radioactive
- yes
- Discovery
- 1944, Glenn T. Seaborg et al.
Origin of the name
In honor of Pierre and Marie Curie.
What does curium look like?
A hard, dense (about 13.5 g/cm³), silvery metal that tarnishes in air. It has only been obtained as a metal in very small quantities. Its compounds are often fluorescent.
Where is curium found?
It does not exist in nature in measurable amounts. It is found in spent nuclear fuel, where it forms through successive neutron captures starting from uranium and plutonium.
How is curium produced?
It is produced by irradiating plutonium or americium for long periods in high-flux neutron reactors, then separated chemically. A tonne of spent fuel contains about twenty grams of it.
Top producers
- United States (Oak Ridge)
- Russia (Dimitrovgrad)
What is curium used for?
- Alpha particle source for the APXS spectrometers on Mars rovers and the Philae lander
- Raw material for making heavier elements (berkelium, californium)
- Target for synthesizing superheavy elements such as livermorium
- Heat source considered for space generators
In everyday life
- None — but it helped analyze the chemistry of Martian soil
Role in living things
No biological role. If it enters the body, it concentrates in the bones, liver and lungs.
Hazards of curium
Highly radiotoxic, an alpha emitter and sometimes a neutron emitter. It is handled in shielded hot cells.
Cosmic origin
- Human-made: Does not exist (or barely) in nature: synthesized in a reactor or accelerator.
History of curium
Glenn Seaborg, Ralph James and Albert Ghiorso produced it in the summer of 1944 by bombarding plutonium-239 with alpha particles (helium nuclei) in the Berkeley cyclotron, then identified it in Chicago. The name curium echoes gadolinium, just above it and named after a scientist, Johan Gadolin.
Did you know?
- Like americium, its discovery was revealed in 1945 on the radio, on the children's show “Quiz Kids.”
- The spectrometer of the little Sojourner rover (1997), and later those of Spirit, Opportunity and Curiosity, contained curium-244.
- Marie Curie shares with Lise Meitner (meitnerium) the rare honor of being a woman who gave her name to an element.
Isotopes of curium
No stable isotopes; curium, intensely radioactive, is produced in reactors. It gives off so much heat that it glows in the dark.
- curium-242: radioactive, half-life 163 days. The element's first synthesized isotope, in 1944.
- curium-244: radioactive, half-life 18.1 years. The alpha source in the spectrometers that analyze rocks on Mars.
- curium-247: radioactive, half-life 1.56 × 10⁷ years. The longest-lived.
- curium-248: radioactive, half-life 348,000 years. The target used to create livermorium.
Related elements
Same family (actinides): Actinium (Ac), Thorium (Th), Protactinium (Pa), Uranium (U), Neptunium (Np), Plutonium (Pu), Americium (Am), Berkelium (Bk), Californium (Cf), Einsteinium (Es), Fermium (Fm), Mendelevium (Md), Nobelium (No), Lawrencium (Lr).