Curium (Cm)
Curium is element 96, a actinide in period 7 of the periodic table. At room temperature it is a solid.
Electron configuration [Rn] 5f7 6d1 7s2
Electrons per shell 2, 8, 18, 32, 25, 9, 2
Curium data
| Atomic number | 96 |
|---|---|
| Symbol | Cm |
| Atomic mass | [247] (mass number of the longest-lived isotope) |
| Category | Actinide |
| Group | — (f-block) |
| Period | 7 |
| Block | f |
| State at 25 °C | solid |
| Melting point | 1618 K (1344.9 °C) |
| Boiling point | 3383 K (3109.9 °C) |
| Density | 13.51 g/cm³ |
| Electronegativity (Pauling) | 1.3 |
| Atomic radius | — |
| 1st ionization energy | 581 kJ/mol |
| Electron affinity | — |
| Oxidation states | +3, +4 |
| Common ion charge | 3+ |
| Discovered | 1944 |
Orbital diagram
Each box is one orbital holding up to two electrons of opposite spin. Following Hund’s rule, electrons spread out singly across a subshell before pairing.
Work through curium’s configuration and its ions →
Where curium sits
Curium belongs to the actinides. Its Pauling electronegativity of 1.3 is mid-range; see the electronegativity chart and periodic trends for context. To use its mass in a calculation, try the molar mass calculator.
Curium FAQ
What is the electron configuration of curium?
Curium (Z = 96) has the configuration 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d10 6s2 6p6 5f7 6d1 7s2. In noble-gas shorthand that is [Rn] 5f7 6d1 7s2. This is an exception to the simple Aufbau prediction (1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f8 6s2 6p6 7s2); a half-filled or filled subshell lowers the energy.
How many valence electrons does curium have?
3 (2 outer s + 1 d electrons; 2 in the outermost shell).
What is the atomic mass of curium?
Curium has no stable isotopes. Its most stable known isotope has mass number 247, so tables list [247].
Is curium a metal?
Yes. Curium is a actinide.
What is the charge of a curium ion?
Curium most commonly forms Cm3+.