Properties
Actinides have similar properties to lanthanides. The 6d and 7s electronic shells are filled in actinium and thorium, and the 5f shell is being filled with further increase in atomic number; the 4f shell is filled in the lanthanides. The first experimental evidence for the filling of the 5f shell in actinides was obtained by McMillan and Abelson in 1940. As in lanthanides (see lanthanide contraction), the ionic radius of actinides monotonically decreases with atomic number (see also Aufbau principle).
| Property | Ac | Th | Pa | U | Np | Pu | Am | Cm | Bk | Cf | Es | Fm | Md | No | Lr |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Core charge | 89 | 90 | 91 | 92 | 93 | 94 | 95 | 96 | 97 | 98 | 99 | 100 | 101 | 102 | 103 |
| atomic mass | 232.0381 | 231.03588 | 238.02891 | ||||||||||||
| Number of natural isotopes | 3 | 9 | 5 | 9 | 4 | 5 | 5 | 8 | 2 | 5 | — | — | — | — | — |
| Natural isotopes | 225, 227–228 | 226–232, 234–235 | 231, 233–236 | 232–240 | 237–240 | 238–240, 242, 244 | 241–245 | 242–249 | 249–250 | 249–253 | — | — | — | — | — |
| Longest-lived isotope | 227 | 232 | 231 | 238 | 237 | 244 | 243 | 247 | 247 | 251 | 252 | 257 | 258 | 259 | 262 |
| Half-life of the longest-lived isotope | 21.8 years | 14 billion years | 32,500 years | 4.47 billion years | 2.14 million years | 80.8 million years | 7,370 years | 15.6 million years | 1,400 years | 900 years | 1.29 years | 100.5 days | 52 days | 58 min | 261 min |
| Electronic configuration in the ground state | 6d17s2 | 6d27s2 | 5f26d17s2or 5f16d27s2 | 5f36d17s2 | 5f46d17s2or 5f57s2 | 5f67s2 | 5f77s2 | 5f76d17s2 | 5f97s2or 5f86d17s2 | 5f107s2 | 5f117s2 | 5f127s2 | 5f137s2 | 5f147s2 | 5f147s27p1 |
| Oxidation state | 3 | 3, 4 | 3, 4, 5 | 3, 4, 5, 6 | 3, 4, 5, 6, 7 | 3, 4, 5, 6, 7 | 2, 3, 4 | 3, 4 | 3, 4 | 2, 3 | 2, 3 | 2, 3 | 2, 3 | 2, 3 | 3 |
| Metallic radius, nm | 0.203 | 0.180 | 0.162 | 0.153 | 0.150 | 0.162 | 0.173 | 0.174 | 0.170 | 0.186 | 0.186 | — | — | — | — |
| Ionic radius, nm: An4+ An3+ |
— 0.126 |
0.114 — |
0.104 0.118 |
0.103 0.118 |
0.101 0.116 |
0.100 0.115 |
0.099 0.114 |
0.099 0.112 |
0.097 0.110 |
0.096 0.109 |
0.085 0.098 |
0.084 0.091 |
0.084 0.090 |
0.084 0.095 |
0.083 0.088 |
| Temperature, °C: melting boiling |
1050 3300 |
1750 4800 |
1572 4400 |
1130 3800 |
640 3900 |
640 3230 |
1176 2610 |
1340 — |
1050 — |
900 — |
860 — |
1530 — |
830 — |
830 — |
1630 — |
| Density, g/cm3 | 10.07 | 11.78 | 15.37 | 19.06 | 20.25 | 19.84 | 11.7 | 13.51 | 14.78 | 15.1 | 8.84 | ||||
| Standard electrode potential, V: E° (An4+/An0) E° (An3+/An0) |
— −2.13 |
−1.83 — |
−1.47 — |
−1.38 −1.66 |
−1.30 −1.79 |
−1.25 −2.00 |
−0.90 −2.07 |
−0.75 −2.06 |
−0.55 −1.96 |
−0.59 −1.97 |
−0.36 −1.98 |
−0.29 −1.96 |
— −1.74 |
— −1.20 |
- −2.10 |
| Color 4+ 3+ |
— Colorless |
Colorless Blue |
Yellow Dark blue |
Green Purple |
Yellow-green Purple |
Brown Violet |
Red Rose |
Yellow Colorless |
Beige Yellow-green |
Green Green |
— Pink |
— — |
— — |
— — |
— — |
| Oxidation state | 89 | 90 | 91 | 92 | 93 | 94 | 95 | 96 | 97 | 98 | 99 |
| +3 | Ac3+ | Th3+ | Pa3+ | U3+ | Np3+ | Pu3+ | Am3+ | Cm3+ | Bk3+ | Cf3+ | Es3+ |
| +4 | Th4+ | Pa4+ | U4+ | Np4+ | Pu4+ | Am4+ | Cm4+ | Bk4+ | Cf4+ | ||
| +5 | PaO+ 2 |
UO+ 2 |
NpO+ 2 |
PuO+ 2 |
AmO+ 2 |
||||||
| +6 | UO2+ 2 |
NpO2+ 2 |
PuO2+ 2 |
AmO2+ 2 |
|||||||
| +7 | NpO3+ 2 |
PuO3+ 2 |
5- |
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