Element: Berkelium
General data
| Element name | Berkelium |
|---|---|
| Chemical symbol | Bk |
| Atomic number Z | 97 |
| Year discovered | 1949 |
| Standard state (25°C) | Solid |
| Category | Actinide |
| Block | f |
| Atomic mass | [247] |
| CPK color | #8A4FE3 |
Physical properties
| Melting point | 1323 K (1050 °C) |
|---|---|
| Boiling point | no data |
| Density | 14 g/cm³ |
Energy properties
| First ionization energy | 6.23 eV |
|---|---|
| Electron affinity | no data |
Atomic structure
| Protons | 97 (Atomic number) |
|---|---|
| Neutrons (Bk-247, longest-lived isotope) | 150 |
| Electrons | 97 |
| Electron configuration | [Rn] 7s² 5f⁹ |
| Oxidation states | +4, +3 |
| Electronegativity (Pauling) | 1.3 |
| Atomic radius (van der Waals) | 244 pm |
Ionization energies - NIST ASD (97 states)
| State | Charge | Ioniz. energy (eV) | Type |
|---|---|---|---|
| Bk I | 0+ | 6.19785 ± 0.00025 | measured |
| Bk II | 1+ | 11.9 ± 0.4 | semi-empirical |
| Bk III | 2+ | 21.6 ± 0.4 | semi-empirical |
| Bk IV | 3+ | 36 ± 0.4 | semi-empirical |
| Bk V | 4+ | 56 ± 1.9 | calculated |
| Bk VI | 5+ | 70.1 ± 2 | calculated |
| Bk VII | 6+ | 90 ± 2 | calculated |
| Bk VIII | 7+ | 114 ± 6 | calculated |
| Bk IX | 8+ | 130 ± 6 | calculated |
| Bk X | 9+ | 147 ± 7 | calculated |
| Bk XI | 10+ | 171 ± 9 | calculated |
| Bk XII | 11+ | 195 ± 10 | calculated |
| Bk XIII | 12+ | 218 ± 11 | calculated |
| Bk XIV | 13+ | 240 ± 12 | calculated |
| Bk XV | 14+ | 259 ± 12 | calculated |
| Bk XVI | 15+ | 279 ± 14 | calculated |
| Bk XVII | 16+ | 303 ± 15 | calculated |
| Bk XVIII | 17+ | 339 ± 3 | calculated |
| Bk XIX | 18+ | 361 ± 3 | calculated |
| Bk XX | 19+ | 497 ± 4 | calculated |
| Bk XXI | 20+ | 526 ± 4 | calculated |
| Bk XXII | 21+ | 557 ± 4 | calculated |
| Bk XXIII | 22+ | 590 ± 4 | calculated |
| Bk XXIV | 23+ | 621 ± 4 | calculated |
| Bk XXV | 24+ | 652 ± 4 | calculated |
| Bk XXVI | 25+ | 700 ± 4 | calculated |
| Bk XXVII | 26+ | 733 ± 4 | calculated |
| Bk XXVIII | 27+ | 768 ± 4 | calculated |
| Bk XXIX | 28+ | 800 ± 4 | calculated |
| Bk XXX | 29+ | 960 ± 50 | calculated |
| Bk XXXI | 30+ | 1000 ± 50 | calculated |
| Bk XXXII | 31+ | 1040 ± 50 | calculated |
| Bk XXXIII | 32+ | 1080 ± 50 | calculated |
| Bk XXXIV | 33+ | 1200 ± 60 | calculated |
| Bk XXXV | 34+ | 1240 ± 60 | calculated |
| Bk XXXVI | 35+ | 1360 ± 70 | calculated |
| Bk XXXVII | 36+ | 1410 ± 70 | calculated |
| Bk XXXVIII | 37+ | 1550 ± 80 | calculated |
| Bk XXXIX | 38+ | 1630 ± 80 | calculated |
| Bk XL | 39+ | 1720 ± 90 | calculated |
| Bk XLI | 40+ | 1800 ± 90 | calculated |
| Bk XLII | 41+ | 1890 ± 90 | calculated |
| Bk XLIII | 42+ | 1970 ± 100 | calculated |
| Bk XLIV | 43+ | 2050 ± 100 | calculated |
| Bk XLV | 44+ | 2140 ± 110 | calculated |
| Bk XLVI | 45+ | 2240 ± 110 | calculated |
| Bk XLVII | 46+ | 2320 ± 120 | calculated |
| Bk XLVIII | 47+ | 2410 ± 120 | calculated |
| Bk XLIX | 48+ | 2490 ± 120 | calculated |
| Bk L | 49+ | 2580 ± 120 | calculated |
| Bk LI | 50+ | 2670 ± 140 | calculated |
| Bk LII | 51+ | 3080 ± 4 | calculated |
| Bk LIII | 52+ | 3154 ± 4 | calculated |
| Bk LIV | 53+ | 3232 ± 5 | calculated |
| Bk LV | 54+ | 3315 ± 5 | calculated |
| Bk LVI | 55+ | 3393 ± 5 | calculated |
| Bk LVII | 56+ | 3469 ± 5 | calculated |
| Bk LVIII | 57+ | 3630 ± 6 | calculated |
| Bk LIX | 58+ | 3709 ± 6 | calculated |
| Bk LX | 59+ | 3797 ± 7 | calculated |
| Bk LXI | 60+ | 3877 ± 10 | calculated |
| Bk LXII | 61+ | 4202 ± 12 | calculated |
| Bk LXIII | 62+ | 4281 ± 15 | calculated |
| Bk LXIV | 63+ | 4365 ± 19 | calculated |
| Bk LXV | 64+ | 4445 ± 24 | calculated |
| Bk LXVI | 65+ | 4940 ± 30 | calculated |
| Bk LXVII | 66+ | 5040 ± 40 | calculated |
| Bk LXVIII | 67+ | 5270 ± 40 | calculated |
| Bk LXIX | 68+ | 5360 ± 50 | calculated |
| Bk LXX | 69+ | 8500 ± 50 | calculated |
| Bk LXXI | 70+ | 8670 ± 60 | calculated |
| Bk LXXII | 71+ | 8850 ± 60 | calculated |
| Bk LXXIII | 72+ | 9050 ± 70 | calculated |
| Bk LXXIV | 73+ | 9240 ± 90 | calculated |
| Bk LXXV | 74+ | 9420 ± 90 | calculated |
| Bk LXXVI | 75+ | 9880 ± 100 | calculated |
| Bk LXXVII | 76+ | 10070 ± 110 | calculated |
| Bk LXXVIII | 77+ | 10280 ± 120 | calculated |
| Bk LXXIX | 78+ | 10480 ± 120 | calculated |
| Bk LXXX | 79+ | 11020 ± 140 | calculated |
| Bk LXXXI | 80+ | 11190 ± 150 | calculated |
| Bk LXXXII | 81+ | 11380 ± 160 | calculated |
| Bk LXXXIII | 82+ | 11550 ± 170 | calculated |
| Bk LXXXIV | 83+ | 13090 ± 190 | calculated |
| Bk LXXXV | 84+ | 13300 ± 200 | calculated |
| Bk LXXXVI | 85+ | 13720 ± 220 | calculated |
| Bk LXXXVII | 86+ | 13910 ± 240 | calculated |
| Bk LXXXVIII | 87+ | 28380 ± 250 | calculated |
| Bk LXXXIX | 88+ | 28800 ± 300 | calculated |
| Bk XC | 89+ | 29300 ± 300 | calculated |
| Bk XCI | 90+ | 29800 ± 300 | calculated |
| Bk XCII | 91+ | 35500 ± 300 | calculated |
| Bk XCIII | 92+ | 36200 ± 400 | calculated |
| Bk XCIV | 93+ | 37000 ± 400 | calculated |
| Bk XCV | 94+ | 37457.6 ± 0.9 | calculated |
| Bk XCVI | 95+ | 146917 ± 5 | calculated |
| Bk XCVII | 96+ | 149398 ± 5 | 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 (20)
| A | N | Half-life | Decay |
|---|---|---|---|
| Bk-233 | 136 | 20 s | α |
| Bk-234 | 137 | 19 s | α |
| Bk-236 | 139 | 22 s | EC/β⁺ |
| Bk-237 | 140 | unknown | EC/β⁺ |
| Bk-238 | 141 | 144 s | EC/β⁺ |
| Bk-239 | 142 | unknown | EC/β⁺ |
| Bk-240 | 143 | 4.8 min | EC/β⁺ |
| Bk-241 | 144 | 4.6 min | EC/β⁺ |
| Bk-242 | 145 | 7.0 min | EC/β⁺ |
| Bk-243 | 146 | 4.6 h | EC/β⁺ |
| Bk-244 | 147 | 5.02 h | EC/β⁺ |
| Bk-245 | 148 | 4.96 d | EC |
| Bk-246 | 149 | 1.80 d | EC/β⁺ |
| Bk-247 | 150 | 1400 a | α |
| Bk-248 | 151 | > 9 a | α |
| Bk-249 | 152 | 327.2 d | β⁻ |
| Bk-250 | 153 | 3.212 h | β⁻ |
| Bk-251 | 154 | 56.0 min | β⁻ |
| Bk-252 | 155 | 1.8 min | β⁻ |
| Bk-253 | 156 | > 10 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