ElementsWhat is curium?
Curium is a radioactive, silvery metal made in reactors. It is so radioactive that it glows in the dark.
What is curium used for?
Research, and the X-ray instruments carried by some Mars rovers.
Where the name comes from
In honour of Marie and Pierre Curie.
Key facts
- Symbol
- Cm
- Atomic number
- 96
- Atomic mass
- 247.07035 u
- Family
- Actinide
- Period
- 7
- Group
- none (f-block)
- Block
- f
- State at room temperature
- Solid
- Melting point
- 1,345 °C (1,618 K, 2,453 °F)
- Boiling point
- 3,127 °C (3,400 K, 5,660 °F)
- Density
- 13.51 g/cm³
- Electrons per shell
- 2, 8, 18, 32, 25, 9, 2
- Electron configuration
- [Rn]7s2 5f7 6d1
- Common oxidation states
- +3
- Electronegativity (Pauling)
- 1.3
- First ionisation energy
- 6.02 eV
- Electron affinity
- no value
- Atomic radius (van der Waals)
- 245 pm
- Discovered
- 1944
Place in the periodic table
Curium is element number 96. It sits in period 7 (row 7) of the periodic table, in the separate row of actinides drawn below the main table, and belongs to the f-block. Just before it comes americium (95), and just after it comes berkelium (97).
Family: Actinides.
Physical properties
At room temperature curium is a solid. It melts at 1,345 °C and boils at 3,127 °C, so it stays liquid over a range of 1,782 degrees. Its density is 13.51 grams per cubic centimetre, so a one-litre block would weigh about 13.51 kilograms. By density it ranks 15th among the 96 elements with a measured value.
Inside the atom
An atom of curium has 96 protons in its nucleus and, when neutral, 96 electrons around it. The electrons are arranged in 7 shells: 2, 8, 18, 32, 25, 9, 2. The outermost shell holds 2 electrons. Written in full, the electron configuration is [Rn]7s2 5f7 6d1.
Its electronegativity on the Pauling scale is 1.3. This number shows how strongly an atom pulls shared electrons towards itself: fluorine, the strongest, is 3.98. Removing one electron from an atom takes 6.02 electronvolts (about 581 kilojoules per mole). One mole of curium weighs 247.07035 grams, so a single gram contains about 2.44 × 1021 atoms.
The ring picture is a simple model that only counts the electrons in each shell. Real atoms do not look like this.
Next steps
- Work out the weight of a compound that contains curium with the molar mass calculator.
- Compare it with every other element in the sortable list.
- Test yourself with the symbol quiz.
Figures on this page are from PubChem (U.S. National Library of Medicine), as downloaded on 11 November 2026. See About and data sources.