Element: Americium
General data
| Element name | Americium |
|---|---|
| Chemical symbol | Am |
| Atomic number Z | 95 |
| Year discovered | 1944 |
| Standard state (25°C) | Solid |
| Category | Actinide |
| Block | f |
| Atomic mass | [243] |
| CPK color | #545CF2 |
Physical properties
| Melting point | 1449 K (1176 °C) |
|---|---|
| Boiling point | 2284 K (2011 °C) |
| Density | 13.69 g/cm³ |
Energy properties
| First ionization energy | 5.993 eV |
|---|---|
| Electron affinity | no data |
Atomic structure
| Protons | 95 (Atomic number) |
|---|---|
| Neutrons (Am-243, longest-lived isotope) | 148 |
| Electrons | 95 |
| Electron configuration | [Rn] 7s² 5f⁷ |
| Oxidation states | +6, +5, +4, +3 |
| Electronegativity (Pauling) | 1.3 |
| Atomic radius (van der Waals) | 244 pm |
Ionization energies - NIST ASD (95 states)
| State | Charge | Ioniz. energy (eV) | Type |
|---|---|---|---|
| Am I | 0+ | 5.97381 ± 0.00025 | measured |
| Am II | 1+ | 11.7 ± 0.4 | semi-empirical |
| Am III | 2+ | 21.7 ± 0.4 | semi-empirical |
| Am IV | 3+ | 36.8 ± 0.4 | semi-empirical |
| Am V | 4+ | 50 ± 1.9 | calculated |
| Am VI | 5+ | 67.9 ± 2 | calculated |
| Am VII | 6+ | 95 ± 5 | calculated |
| Am VIII | 7+ | 110 ± 6 | calculated |
| Am IX | 8+ | 125 ± 6 | calculated |
| Am X | 9+ | 141 ± 7 | calculated |
| Am XI | 10+ | 163 ± 8 | calculated |
| Am XII | 11+ | 184 ± 9 | calculated |
| Am XIII | 12+ | 206 ± 10 | calculated |
| Am XIV | 13+ | 225 ± 3 | calculated |
| Am XV | 14+ | 242 ± 3 | calculated |
| Am XVI | 15+ | 284 ± 3 | calculated |
| Am XVII | 16+ | 305 ± 3 | calculated |
| Am XVIII | 17+ | 424 ± 3 | calculated |
| Am XIX | 18+ | 451 ± 3 | calculated |
| Am XX | 19+ | 481 ± 4 | calculated |
| Am XXI | 20+ | 511 ± 4 | calculated |
| Am XXII | 21+ | 541 ± 4 | calculated |
| Am XXIII | 22+ | 571 ± 4 | calculated |
| Am XXIV | 23+ | 616 ± 4 | calculated |
| Am XXV | 24+ | 646 ± 4 | calculated |
| Am XXVI | 25+ | 680 ± 4 | calculated |
| Am XXVII | 26+ | 711 ± 4 | calculated |
| Am XXVIII | 27+ | 870 ± 40 | calculated |
| Am XXIX | 28+ | 900 ± 50 | calculated |
| Am XXX | 29+ | 940 ± 50 | calculated |
| Am XXXI | 30+ | 980 ± 50 | calculated |
| Am XXXII | 31+ | 1090 ± 50 | calculated |
| Am XXXIII | 32+ | 1130 ± 60 | calculated |
| Am XXXIV | 33+ | 1240 ± 60 | calculated |
| Am XXXV | 34+ | 1280 ± 60 | calculated |
| Am XXXVI | 35+ | 1410 ± 70 | calculated |
| Am XXXVII | 36+ | 1490 ± 70 | calculated |
| Am XXXVIII | 37+ | 1570 ± 80 | calculated |
| Am XXXIX | 38+ | 1650 ± 90 | calculated |
| Am XL | 39+ | 1730 ± 90 | calculated |
| Am XLI | 40+ | 1820 ± 90 | calculated |
| Am XLII | 41+ | 1900 ± 90 | calculated |
| Am XLIII | 42+ | 1980 ± 100 | calculated |
| Am XLIV | 43+ | 2070 ± 100 | calculated |
| Am XLV | 44+ | 2160 ± 110 | calculated |
| Am XLVI | 45+ | 2240 ± 110 | calculated |
| Am XLVII | 46+ | 2320 ± 110 | calculated |
| Am XLVIII | 47+ | 2410 ± 120 | calculated |
| Am XLIX | 48+ | 2480 ± 120 | calculated |
| Am L | 49+ | 2874 ± 4 | calculated |
| Am LI | 50+ | 2946 ± 4 | calculated |
| Am LII | 51+ | 3021 ± 4 | calculated |
| Am LIII | 52+ | 3101 ± 4 | calculated |
| Am LIV | 53+ | 3178 ± 5 | calculated |
| Am LV | 54+ | 3251 ± 5 | calculated |
| Am LVI | 55+ | 3402 ± 5 | calculated |
| Am LVII | 56+ | 3479 ± 5 | calculated |
| Am LVIII | 57+ | 3563 ± 6 | calculated |
| Am LIX | 58+ | 3641 ± 6 | calculated |
| Am LX | 59+ | 3956 ± 7 | calculated |
| Am LXI | 60+ | 4033 ± 10 | calculated |
| Am LXII | 61+ | 4115 ± 12 | calculated |
| Am LXIII | 62+ | 4191 ± 15 | calculated |
| Am LXIV | 63+ | 4642 ± 19 | calculated |
| Am LXV | 64+ | 4733 ± 24 | calculated |
| Am LXVI | 65+ | 4960 ± 30 | calculated |
| Am LXVII | 66+ | 5050 ± 40 | calculated |
| Am LXVIII | 67+ | 8040 ± 40 | calculated |
| Am LXIX | 68+ | 8210 ± 50 | calculated |
| Am LXX | 69+ | 8390 ± 50 | calculated |
| Am LXXI | 70+ | 8590 ± 60 | calculated |
| Am LXXII | 71+ | 8770 ± 60 | calculated |
| Am LXXIII | 72+ | 8950 ± 70 | calculated |
| Am LXXIV | 73+ | 9380 ± 90 | calculated |
| Am LXXV | 74+ | 9560 ± 90 | calculated |
| Am LXXVI | 75+ | 9770 ± 100 | calculated |
| Am LXXVII | 76+ | 9960 ± 110 | calculated |
| Am LXXVIII | 77+ | 10490 ± 120 | calculated |
| Am LXXIX | 78+ | 10650 ± 120 | calculated |
| Am LXXX | 79+ | 10830 ± 140 | calculated |
| Am LXXXI | 80+ | 11000 ± 150 | calculated |
| Am LXXXII | 81+ | 12400 ± 160 | calculated |
| Am LXXXIII | 82+ | 12600 ± 170 | calculated |
| Am LXXXIV | 83+ | 13000 ± 190 | calculated |
| Am LXXXV | 84+ | 13190 ± 200 | calculated |
| Am LXXXVI | 85+ | 27110 ± 220 | calculated |
| Am LXXXVII | 86+ | 27550 ± 240 | calculated |
| Am LXXXVIII | 87+ | 28040 ± 250 | calculated |
| Am LXXXIX | 88+ | 28500 ± 300 | calculated |
| Am XC | 89+ | 33700 ± 300 | calculated |
| Am XCI | 90+ | 34300 ± 300 | calculated |
| Am XCII | 91+ | 35100 ± 300 | calculated |
| Am XCIII | 92+ | 35549.4 ± 0.7 | calculated |
| Am XCIV | 93+ | 139769.5 ± 0.7 | calculated |
| Am XCV | 94+ | 142153.5 ± 0.9 | 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 |
|---|---|---|---|
| Am-223 | 128 | 5 ms | α |
| Am-229 | 134 | 0.9 s | α |
| Am-230 | 135 | 36 s | EC/β⁺ |
| Am-232 | 137 | 1.31 min | EC/β⁺ |
| Am-233 | 138 | 3.2 min | EC/β⁺ |
| Am-234 | 139 | 2.32 min | EC/β⁺ |
| Am-235 | 140 | 10.3 min | EC/β⁺ |
| Am-236 | 141 | 3.6 min | EC/β⁺ |
| Am-237 | 142 | 73 min | EC/β⁺ |
| Am-238 | 143 | 97.4 min | EC/β⁺ |
| Am-239 | 144 | 11.9 h | EC |
| Am-240 | 145 | 50.9 h | EC/β⁺ |
| Am-241 | 146 | 432.6 a | α |
| Am-242 | 147 | 16.02 h | β⁻ |
| Am-243 | 148 | 7345 a | α |
| Am-244 | 149 | 10.02 h | β⁻ |
| Am-245 | 150 | 2.047 h | β⁻ |
| Am-246 | 151 | 39 min | β⁻ |
| Am-247 | 152 | 23.0 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