Element: Curium
General data
| Element name | Curium |
|---|---|
| Chemical symbol | Cm |
| Atomic number Z | 96 |
| Year discovered | 1944 |
| Standard state (25°C) | Solid |
| Category | Actinide |
| Block | f |
| Atomic mass | [247] |
| CPK color | #785CE3 |
Physical properties
| Melting point | 1618 K (1345 °C) |
|---|---|
| Boiling point | 3400 K (3127 °C) |
| Density | 13.51 g/cm³ |
Energy properties
| First ionization energy | 6.02 eV |
|---|---|
| Electron affinity | no data |
Atomic structure
| Protons | 96 (Atomic number) |
|---|---|
| Neutrons (Cm-247, longest-lived isotope) | 151 |
| Electrons | 96 |
| Electron configuration | [Rn] 7s² 5f⁷ 6d¹ |
| Oxidation states | +3 |
| Electronegativity (Pauling) | 1.3 |
| Atomic radius (van der Waals) | 245 pm |
Ionization energies - NIST ASD (96 states)
| State | Charge | Ioniz. energy (eV) | Type |
|---|---|---|---|
| Cm I | 0+ | 5.992241 ± 0.00002 | measured |
| Cm II | 1+ | 12.4 ± 0.4 | semi-empirical |
| Cm III | 2+ | 20.1 ± 0.4 | semi-empirical |
| Cm IV | 3+ | 37.7 ± 0.4 | semi-empirical |
| Cm V | 4+ | 51 ± 1.9 | calculated |
| Cm VI | 5+ | 69.1 ± 2 | calculated |
| Cm VII | 6+ | 97 ± 5 | calculated |
| Cm VIII | 7+ | 112 ± 6 | calculated |
| Cm IX | 8+ | 128 ± 6 | calculated |
| Cm X | 9+ | 144 ± 7 | calculated |
| Cm XI | 10+ | 167 ± 8 | calculated |
| Cm XII | 11+ | 190 ± 10 | calculated |
| Cm XIII | 12+ | 213 ± 11 | calculated |
| Cm XIV | 13+ | 235 ± 12 | calculated |
| Cm XV | 14+ | 253 ± 12 | calculated |
| Cm XVI | 15+ | 272 ± 14 | calculated |
| Cm XVII | 16+ | 311 ± 3 | calculated |
| Cm XVIII | 17+ | 332 ± 3 | calculated |
| Cm XIX | 18+ | 460 ± 3 | calculated |
| Cm XX | 19+ | 489 ± 4 | calculated |
| Cm XXI | 20+ | 518 ± 4 | calculated |
| Cm XXII | 21+ | 550 ± 4 | calculated |
| Cm XXIII | 22+ | 580 ± 4 | calculated |
| Cm XXIV | 23+ | 611 ± 4 | calculated |
| Cm XXV | 24+ | 657 ± 4 | calculated |
| Cm XXVI | 25+ | 689 ± 4 | calculated |
| Cm XXVII | 26+ | 723 ± 4 | calculated |
| Cm XXVIII | 27+ | 755 ± 4 | calculated |
| Cm XXIX | 28+ | 910 ± 50 | calculated |
| Cm XXX | 29+ | 950 ± 50 | calculated |
| Cm XXXI | 30+ | 990 ± 50 | calculated |
| Cm XXXII | 31+ | 1030 ± 50 | calculated |
| Cm XXXIII | 32+ | 1140 ± 60 | calculated |
| Cm XXXIV | 33+ | 1180 ± 60 | calculated |
| Cm XXXV | 34+ | 1300 ± 60 | calculated |
| Cm XXXVI | 35+ | 1340 ± 70 | calculated |
| Cm XXXVII | 36+ | 1480 ± 70 | calculated |
| Cm XXXVIII | 37+ | 1560 ± 80 | calculated |
| Cm XXXIX | 38+ | 1650 ± 80 | calculated |
| Cm XL | 39+ | 1730 ± 90 | calculated |
| Cm XLI | 40+ | 1810 ± 90 | calculated |
| Cm XLII | 41+ | 1890 ± 90 | calculated |
| Cm XLIII | 42+ | 1980 ± 100 | calculated |
| Cm XLIV | 43+ | 2060 ± 100 | calculated |
| Cm XLV | 44+ | 2160 ± 110 | calculated |
| Cm XLVI | 45+ | 2240 ± 110 | calculated |
| Cm XLVII | 46+ | 2320 ± 120 | calculated |
| Cm XLVIII | 47+ | 2410 ± 120 | calculated |
| Cm XLIX | 48+ | 2490 ± 120 | calculated |
| Cm L | 49+ | 2580 ± 120 | calculated |
| Cm LI | 50+ | 2976 ± 4 | calculated |
| Cm LII | 51+ | 3050 ± 4 | calculated |
| Cm LIII | 52+ | 3125 ± 4 | calculated |
| Cm LIV | 53+ | 3207 ± 5 | calculated |
| Cm LV | 54+ | 3284 ± 5 | calculated |
| Cm LVI | 55+ | 3360 ± 5 | calculated |
| Cm LVII | 56+ | 3515 ± 5 | calculated |
| Cm LVIII | 57+ | 3593 ± 6 | calculated |
| Cm LIX | 58+ | 3679 ± 6 | calculated |
| Cm LX | 59+ | 3758 ± 7 | calculated |
| Cm LXI | 60+ | 4078 ± 10 | calculated |
| Cm LXII | 61+ | 4156 ± 12 | calculated |
| Cm LXIII | 62+ | 4239 ± 15 | calculated |
| Cm LXIV | 63+ | 4317 ± 19 | calculated |
| Cm LXV | 64+ | 4791 ± 24 | calculated |
| Cm LXVI | 65+ | 4880 ± 30 | calculated |
| Cm LXVII | 66+ | 5110 ± 40 | calculated |
| Cm LXVIII | 67+ | 5200 ± 40 | calculated |
| Cm LXIX | 68+ | 8270 ± 50 | calculated |
| Cm LXX | 69+ | 8440 ± 50 | calculated |
| Cm LXXI | 70+ | 8620 ± 60 | calculated |
| Cm LXXII | 71+ | 8820 ± 60 | calculated |
| Cm LXXIII | 72+ | 9000 ± 70 | calculated |
| Cm LXXIV | 73+ | 9180 ± 90 | calculated |
| Cm LXXV | 74+ | 9630 ± 90 | calculated |
| Cm LXXVI | 75+ | 9820 ± 100 | calculated |
| Cm LXXVII | 76+ | 10020 ± 110 | calculated |
| Cm LXXVIII | 77+ | 10220 ± 120 | calculated |
| Cm LXXIX | 78+ | 10760 ± 120 | calculated |
| Cm LXXX | 79+ | 10920 ± 140 | calculated |
| Cm LXXXI | 80+ | 11100 ± 150 | calculated |
| Cm LXXXII | 81+ | 11270 ± 160 | calculated |
| Cm LXXXIII | 82+ | 12740 ± 170 | calculated |
| Cm LXXXIV | 83+ | 12950 ± 190 | calculated |
| Cm LXXXV | 84+ | 13350 ± 200 | calculated |
| Cm LXXXVI | 85+ | 13550 ± 220 | calculated |
| Cm LXXXVII | 86+ | 27740 ± 240 | calculated |
| Cm LXXXVIII | 87+ | 28180 ± 250 | calculated |
| Cm LXXXIX | 88+ | 28700 ± 300 | calculated |
| Cm XC | 89+ | 29100 ± 300 | calculated |
| Cm XCI | 90+ | 34600 ± 300 | calculated |
| Cm XCII | 91+ | 35200 ± 300 | calculated |
| Cm XCIII | 92+ | 36000 ± 400 | calculated |
| Cm XCIV | 93+ | 36493 ± 0.9 | calculated |
| Cm XCV | 94+ | 143311 ± 4 | calculated |
| Cm XCVI | 95+ | 145740.1 ± 1.6 | calculated |
Value type as given by NIST ASD: measured - from evaluated experimental data; calculated - from ab initio calculations (mostly highly ionised atoms that have not been measured; for the simplest ones, e.g. H I, the calculation is more accurate than measurement); semi-empirical - from interpolation, extrapolation or another semi-empirical method.
Photos
Isotopes (19)
| A | N | Half-life | Decay |
|---|---|---|---|
| Cm-233 | 137 | 23 s | α |
| Cm-234 | 138 | 50 s | α |
| Cm-235 | 139 | 300 s | EC/β⁺ |
| Cm-236 | 140 | 6.8 min | EC/β⁺ |
| Cm-237 | 141 | unknown | EC/β⁺ |
| Cm-238 | 142 | 2.2 h | EC |
| Cm-239 | 143 | 2.5 h | EC/β⁺ |
| Cm-240 | 144 | 30 d | α |
| Cm-241 | 145 | 32.8 d | EC |
| Cm-242 | 146 | 162.88 d | α |
| Cm-243 | 147 | 29.18 a | α |
| Cm-244 | 148 | 18.11 a | α |
| Cm-245 | 149 | 8250 a | α |
| Cm-246 | 150 | 4760 a | α |
| Cm-247 | 151 | 1.56×10⁷ a | α |
| Cm-248 | 152 | 3.48×10⁵ a | α |
| Cm-249 | 153 | 64.15 min | β⁻ |
| Cm-250 | 154 | ≈ 8300 a | SF |
| Cm-251 | 155 | 16.8 min | β⁻ |
Data sources
- PubChem Periodic Table API - Retrieved on 29 June 2026 - licence: CC0
- IUPAC CIAAW - Abridged Standard Atomic Weights 2024 - Table version: 2024 - licence: Public domain
- NNDC Wallet Cards 2023 - Data as of 15 October 2024 - licence: Public domain
- NIST Atomic Spectra Database (ASD) - Retrieved on 29 June 2026 - licence: © U.S. Secretary of Commerce
- Images of Elements - Retrieved on 29 June 2026 - licence: CC BY 3.0