Curium
[Rn] 5f⁷ 6d¹ 7s² · 2 · 8 · 18 · 32 · 25 · 9 · 2
An actinide named for the Curies. Curium emits alpha particles so intensely that a solution of its salts heats itself and glows pale violet in the dark.
3D model
Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.
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Atomic properties
- Atomic number
- 96
- Atomic mass
- 247 а.е.м. ≈
- Electron configuration
- [Rn] 5f⁷ 6d¹ 7s²
- Electrons per shell
- 2 · 8 · 18 · 32 · 25 · 9 · 2
- Block
- f-block
- Group
- no data
- Period
- 7
- Electronegativity (Pauling)
- 1.28
- Electronegativity (Allen)
- 1.28
- Atomic radius
- 245 pm
- Covalent radius
- 169 pm
- Van der Waals radius
- 245 pm
- Ionisation energy 1
- 581 kJ/mol
- Electron affinity
- 27.2 kJ/mol
- Common oxidation states
- +3
- Oxidation states
- +3, +4, +5, +6, +8
Physical properties
- State at 25 °C
- solid
- Density
- 13.51 g/cm³
- Melting point
- 1 613 K · 1 339.9 °C
- Boiling point
- 3 383 K · 3 109.9 °C ≈
- Speed of sound
- no data
Thermal properties
- Heat of fusion
- 15 kJ/mol
- Heat of vaporisation
- 320 kJ/mol ≈
- Specific heat capacity
- 0.08 J/(g·K)
- Thermal conductivity
- 8.8 W/(m·K)
Mechanical properties
- Young's modulus
- no data
- Shear modulus
- no data
- Bulk modulus
- no data
- Poisson ratio
- no data
- Mohs hardness
- no data
- Brinell hardness
- no data
Electrical and magnetic properties
- Electrical resistivity
- 1 250 nΩ·m
- Magnetic ordering
- antiferromagnetic
- Curie point
- no data
- Néel point
- 65 K
- Superconducting point
- no data
Crystal structure
- Crystal structure
- hexagonal close-packed (hcp)
- Lattice constants
- a = 349.6 pm · c = 1 133.1 pm
Abundance
- In the crust
- 0 mg/kg
- In the ocean
- 0 mg/L
- In the universe
- 0 mg/kg
- In the human body
- 0 mg/kg
Isotopes
| Isotope | Abundance | Half-life | Decay mode |
|---|---|---|---|
| 244Cm | — | 18.09 yr | α |
| 247Cm | — | 15.6 Myr | α |
| 248Cm | — | 347 942.35 yr | α |
Curium-244, half-life 18 years, gives about 3 W of heat per gram. Curium-247, half-life 15.6 million years, is the longest-lived isotope.
Discovery
- Year of discovery
- 1944
- Discovered by
- Seaborg, James and Ghiorso
- Where
- Berkeley, USA
- Origin of the name
- after Marie and Pierre Curie
History
Seaborg, James and Ghiorso synthesised curium in the summer of 1944 at Berkeley by bombarding plutonium with alpha particles. Paradoxically curium was made before americium, despite its higher number.
Where it occurs
Absent from nature.
How it is produced
In reactors by repeated neutron capture. Curium-244 accumulates in spent fuel and contributes noticeably to its heat output after decades of storage.
Role in living things
No biological role.
Safety
Extremely radiotoxic and bone-seeking. It is handled in hot cells.
Uses
- Alpha spectrometers for soil analysis: the APXS instruments on Mars rovers run on curium-244
- Neutron and power sources in spacecraft
- Breeding heavier actinides under reactor irradiation
Curiosities
- The APXS spectrometers on Sojourner, Spirit, Opportunity and Curiosity all measured Martian rock composition using curium-244.
- Curium solutions glow in the dark from their own radioluminescence.
- Curium was synthesised before americium, despite following it in the table.
- Curium is the only element named after a married couple.