Curium (Cm): Electron Configuration, Properties and Uses
Curium (Cm): Electron Configuration, Properties and Uses
Electron configuration [Rn] 7s2 5f7 6d1 · f-block, actinide series · period 7 · Ar [247]
Curium data
- Atomic number
- 96
- Relative atomic mass
- [247]
- Group
- – (actinide series)
- Period
- 7
- Block
- f
- Category
- Actinide
- Electron configuration
- [Rn] 7s2 5f7 6d1
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f7 6d1
- Electrons per shell
- 2, 8, 18, 32, 25, 9, 2 (K L M N O P Q)
- Valence electrons
- 2 (in the outer shell)
- Electronegativity (Pauling)
- 1.3
- First ionisation energy
- 6.02 eV
- Atomic radius (van der Waals)
- 245 pm
- State at room temperature
- Solid
- Melting point
- 1345 °C
- Boiling point
- 3127 °C
- Density
- 13.51 g/cm³
- Common oxidation states
- +3
- Discovered
- 1944
Source: PubChem (NIH, accessed 13 Nov 2026); atomic mass: IUPAC standard atomic weight.
Electron shell diagram
K 2 · L 8 · M 18 · N 32 · O 25 · P 9 · Q 2
Orbital diagram (outer electrons)
About curium
Curium is a chemical element with the symbol Cm and atomic number 96. It belongs to the actinide series in period 7 (f-block), usually shown below the main table. Curium was first discovered in 1944. It is named after Marie and Pierre Curie. Curium is a solid at room temperature, melting at 1345 °C and boiling at 3127 °C.
Curium electron configuration
The electron configuration of curium is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f7 6d1, or in short [Rn] 7s2 5f7 6d1. Its electrons occupy 7 shells: K = 2, L = 8, M = 18, N = 32, O = 25, P = 9, Q = 2. As an actinide, curium fills the 5f subshell. Its outer 7s subshell holds 2 electrons; valence electrons for this series are not assigned by the usual group rule. This is an exception to the Aufbau rule: the usual filling order predicts [Rn] 7s2 5f8, but the 5f and 6d subshells are so close in energy that electrons occupy 6d. When it forms cations, electrons leave the outermost subshell first: Cm3+ = [Rn] 5f7.
Filling order: 1s2(2) → 2s2(4) → 2p6(10) → 3s2(12) → 3p6(18) → 4s2(20) → 3d10(30) → 4p6(36) → 5s2(38) → 4d10(48) → 5p6(54) → 6s2(56) → 4f14(70) → 5d10(80) → 6p6(86) → 7s2(88) → 5f7(95) → 6d1(96)
Uses of curium
The main uses of curium include alpha sources in the alpha particle X-ray spectrometers (APXS) on Mars rovers.
Safety
Curium is radioactive. Using, storing or transporting radioactive material requires a licence from the national regulator (BAPETEN in Indonesia). Always read the safety data sheet (SDS) before working with a chemical.
Other actinides
Frequently asked questions
What is the electron configuration of curium?
The electron configuration of curium (Cm, atomic number 96) is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f7 6d1, or [Rn] 7s2 5f7 6d1 in short. By shell: 2, 8, 18, 32, 25, 9, 2.
How many valence electrons does curium have?
Curium has 2 electrons in its outer shell. For lanthanides and actinides, valence electrons are not assigned by the usual group rule.
Which group and period is curium in?
Curium is in the actinide series, period 7, f-block.
What is the atomic mass of curium?
Curium has no stable isotope, so the mass number of its longest-lived isotope, [247], is given.
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