Curium (Cm)
Actinide · Radioactive · Synthetic
Curium honours Marie and Pierre Curie. This synthetic actinide glows purple in the dark and has powered instruments that sniff the composition of Martian rocks aboard several rovers.
Position on the periodic table
Atomic properties
| Atomic number | 96 |
|---|---|
| Atomic mass | 247 amu |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f7 6d1 |
| Noble gas shorthand | [Rn] 5f7 6d1 7s2 |
| Electrons per shell | 2, 8, 18, 32, 25, 9, 2 |
| Valence electrons (outer shell) | 2 |
| Common oxidation states | +3 |
| Electronegativity (Pauling) | 1.28 |
| Covalent radius (approx.) | 169 pm |
| First ionization energy | 581 kJ/mol |
| Electron affinity | 27.2 kJ/mol |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Density | 13.51 g/cm³ |
| Melting point | 1339.8 °C (1613 K) |
| Boiling point | 3109.8 °C (3383 K) |
| Appearance | silvery metallic, glows purple in the dark |
| Radioactive | Yes |
| Origin | Synthetic (lab-made) |
Electron configuration of curium
Curium's ground-state electron configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f7 6d1, usually shortened to [Rn] 5f7 6d1 7s2. Its electrons occupy 7 shells (2, 8, 18, 32, 25, 9, 2), placing it in period 7 of the f-block. Explore it interactively in the electron configuration calculator.
Uses of curium
- Alpha sources for planetary science instruments
- Research target for making heavier elements
Biological role: None.
Occurrence: Entirely synthetic, made in reactors.
Common compounds of curium
Cm2O3
Curium(III) oxide
History and discovery
Discovered: 1944 — Glenn T. Seaborg. Name origin: Named after Marie and Pierre Curie.
Seaborg, James and Ghiorso created curium in 1944 — chronologically before americium, despite its higher number.
Safety notes
Intensely radioactive; specialist facilities only.
Educational context only — always follow your school's laboratory rules and never handle chemicals without proper supervision. See our disclaimer.
Practice questions
Quick practice: Curium
1. What is the chemical symbol of Curium?
2. What is the atomic number of Curium?
3. Which category does Curium belong to?
4. What is the state of Curium at room temperature?
5. Which period of the periodic table is Curium in?
Curium FAQs
What is the atomic number of curium?
Curium's atomic number is 96 — every curium atom has 96 protons in its nucleus.
What is the symbol for curium?
Cm. Named after Marie and Pierre Curie.
Is curium a metal, nonmetal, or metalloid?
Curium is classified as a actinide.
What state is curium at room temperature?
At about 25 °C, curium is a solid. It melts at 1339.8 °C.
What is curium used for?
Key uses include: alpha sources for planetary science instruments; research target for making heavier elements.
Related elements
Keep working with this element
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