Element: Francium
General data
| Element name | Francium |
|---|---|
| Chemical symbol | Fr |
| Atomic number Z | 87 |
| Year discovered | 1939 |
| Standard state (25°C) | Solid |
| Category | Alkali metal |
| Block | s |
| Atomic mass | [223] |
| CPK color | #420066 |
Physical properties
| Melting point | 300 K (27 °C) |
|---|---|
| Boiling point | no data |
| Density | no data |
Energy properties
| First ionization energy | 3.9 eV |
|---|---|
| Electron affinity | 0.47 eV |
Atomic structure
| Protons | 87 (Atomic number) |
|---|---|
| Neutrons (Fr-223, longest-lived isotope) | 136 |
| Electrons | 87 |
| Electron configuration | [Rn] 7s¹ |
| Oxidation states | +1 |
| Electronegativity (Pauling) | 0.7 |
| Atomic radius (van der Waals) | 348 pm |
Ionization energies - NIST ASD (87 states)
| State | Charge | Ioniz. energy (eV) | Type |
|---|---|---|---|
| Fr I | 0+ | 4.0727411 ± 0.0000011 | measured |
| Fr II | 1+ | 22.4 ± 1.9 | semi-empirical |
| Fr III | 2+ | 33.5 ± 1.5 | semi-empirical |
| Fr IV | 3+ | 39.1 ± 1.7 | calculated |
| Fr V | 4+ | 50 ± 1.9 | calculated |
| Fr VI | 5+ | 67 ± 2 | calculated |
| Fr VII | 6+ | 80 ± 2 | calculated |
| Fr VIII | 7+ | 106 ± 2.1 | calculated |
| Fr IX | 8+ | 120 ± 2.2 | calculated |
| Fr X | 9+ | 179 ± 2.2 | calculated |
| Fr XI | 10+ | 200 ± 2.4 | calculated |
| Fr XII | 11+ | 222.1 ± 2.5 | calculated |
| Fr XIII | 12+ | 245 ± 3 | calculated |
| Fr XIV | 13+ | 269 ± 3 | calculated |
| Fr XV | 14+ | 293 ± 3 | calculated |
| Fr XVI | 15+ | 324 ± 3 | calculated |
| Fr XVII | 16+ | 349 ± 3 | calculated |
| Fr XVIII | 17+ | 375 ± 3 | calculated |
| Fr XIX | 18+ | 400 ± 3 | calculated |
| Fr XX | 19+ | 530 ± 30 | calculated |
| Fr XXI | 20+ | 560 ± 30 | calculated |
| Fr XXII | 21+ | 590 ± 30 | calculated |
| Fr XXIII | 22+ | 620 ± 30 | calculated |
| Fr XXIV | 23+ | 690 ± 30 | calculated |
| Fr XXV | 24+ | 720 ± 40 | calculated |
| Fr XXVI | 25+ | 810 ± 40 | calculated |
| Fr XXVII | 26+ | 850 ± 40 | calculated |
| Fr XXVIII | 27+ | 910 ± 50 | calculated |
| Fr XXIX | 28+ | 980 ± 50 | calculated |
| Fr XXX | 29+ | 1040 ± 50 | calculated |
| Fr XXXI | 30+ | 1110 ± 50 | calculated |
| Fr XXXII | 31+ | 1180 ± 60 | calculated |
| Fr XXXIII | 32+ | 1250 ± 60 | calculated |
| Fr XXXIV | 33+ | 1320 ± 70 | calculated |
| Fr XXXV | 34+ | 1380 ± 70 | calculated |
| Fr XXXVI | 35+ | 1460 ± 70 | calculated |
| Fr XXXVII | 36+ | 1530 ± 80 | calculated |
| Fr XXXVIII | 37+ | 1600 ± 80 | calculated |
| Fr XXXIX | 38+ | 1670 ± 90 | calculated |
| Fr XL | 39+ | 1740 ± 90 | calculated |
| Fr XLI | 40+ | 1810 ± 90 | calculated |
| Fr XLII | 41+ | 2119 ± 4 | calculated |
| Fr XLIII | 42+ | 2182 ± 4 | calculated |
| Fr XLIV | 43+ | 2247 ± 4 | calculated |
| Fr XLV | 44+ | 2317 ± 4 | calculated |
| Fr XLVI | 45+ | 2384 ± 4 | calculated |
| Fr XLVII | 46+ | 2450 ± 4 | calculated |
| Fr XLVIII | 47+ | 2564 ± 4 | calculated |
| Fr XLIX | 48+ | 2631 ± 4 | calculated |
| Fr L | 49+ | 2706 ± 4 | calculated |
| Fr LI | 50+ | 2774 ± 4 | calculated |
| Fr LII | 51+ | 3049 ± 4 | calculated |
| Fr LIII | 52+ | 3115 ± 4 | calculated |
| Fr LIV | 53+ | 3190 ± 5 | calculated |
| Fr LV | 54+ | 3257 ± 5 | calculated |
| Fr LVI | 55+ | 3556 ± 5 | calculated |
| Fr LVII | 56+ | 3635 ± 5 | calculated |
| Fr LVIII | 57+ | 3828 ± 6 | calculated |
| Fr LIX | 58+ | 3907 ± 4 | semi-empirical |
| Fr LX | 59+ | 6365 ± 7 | calculated |
| Fr LXI | 60+ | 6516 ± 10 | calculated |
| Fr LXII | 61+ | 6678 ± 12 | calculated |
| Fr LXIII | 62+ | 6849 ± 15 | calculated |
| Fr LXIV | 63+ | 7013 ± 19 | calculated |
| Fr LXV | 64+ | 7172 ± 24 | calculated |
| Fr LXVI | 65+ | 7500 ± 30 | calculated |
| Fr LXVII | 66+ | 7670 ± 40 | calculated |
| Fr LXVIII | 67+ | 7850 ± 40 | calculated |
| Fr LXIX | 68+ | 8020 ± 50 | calculated |
| Fr LXX | 69+ | 8500 ± 50 | calculated |
| Fr LXXI | 70+ | 8640 ± 60 | calculated |
| Fr LXXII | 71+ | 8800 ± 60 | calculated |
| Fr LXXIII | 72+ | 8950 ± 70 | calculated |
| Fr LXXIV | 73+ | 9890 ± 90 | calculated |
| Fr LXXV | 74+ | 10070 ± 90 | calculated |
| Fr LXXVI | 75+ | 10420 ± 100 | calculated |
| Fr LXXVII | 76+ | 10590 ± 110 | calculated |
| Fr LXXVIII | 77+ | 22330 ± 120 | calculated |
| Fr LXXIX | 78+ | 22730 ± 120 | calculated |
| Fr LXXX | 79+ | 23170 ± 140 | calculated |
| Fr LXXXI | 80+ | 23570 ± 150 | calculated |
| Fr LXXXII | 81+ | 27060 ± 160 | calculated |
| Fr LXXXIII | 82+ | 27590 ± 170 | calculated |
| Fr LXXXIV | 83+ | 28260 ± 190 | calculated |
| Fr LXXXV | 84+ | 28683.4 ± 0.5 | calculated |
| Fr LXXXVI | 85+ | 113821.9 ± 0.5 | calculated |
| Fr LXXXVII | 86+ | 115857.5 ± 0.7 | 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 (37)
| A | N | Half-life | Decay |
|---|---|---|---|
| Fr-197 | 110 | 1 ms | α |
| Fr-198 | 111 | 15 ms | α |
| Fr-199 | 112 | 5 ms | α |
| Fr-200 | 113 | 50 ms | α |
| Fr-201 | 114 | 63 ms | α |
| Fr-202 | 115 | 364 ms | α |
| Fr-203 | 116 | 550 ms | α |
| Fr-204 | 117 | 1.8 s | α |
| Fr-205 | 118 | 3.90 s | α |
| Fr-206 | 119 | ≈ 16 s | α |
| Fr-207 | 120 | 14.8 s | α |
| Fr-208 | 121 | 58.6 s | α |
| Fr-209 | 122 | 50.5 s | α |
| Fr-210 | 123 | 3.18 min | α |
| Fr-211 | 124 | 3.10 min | α |
| Fr-212 | 125 | 20.3 min | α |
| Fr-213 | 126 | 34.17 s | α |
| Fr-214 | 127 | 5.5 ms | α |
| Fr-215 | 128 | 89 ns | α |
| Fr-216 | 129 | 0.70 μs | α |
| Fr-217 | 130 | 22 μs | α |
| Fr-218 | 131 | 1.1 ms | α |
| Fr-219 | 132 | 22 ms | α |
| Fr-220 | 133 | 27.4 s | α |
| Fr-221 | 134 | 4.801 min | α |
| Fr-222 | 135 | 14.2 min | β⁻ |
| Fr-223 | 136 | 21.99 min | β⁻ |
| Fr-224 | 137 | 3.33 min | β⁻ |
| Fr-225 | 138 | 4.0 min | β⁻ |
| Fr-226 | 139 | 49 s | β⁻ |
| Fr-227 | 140 | 2.47 min | β⁻ |
| Fr-228 | 141 | 38 s | β⁻ |
| Fr-229 | 142 | 50.2 s | β⁻ |
| Fr-230 | 143 | 19.1 s | β⁻ |
| Fr-231 | 144 | 17.6 s | β⁻ |
| Fr-232 | 145 | 5.5 s | β⁻ |
| Fr-233 | 146 | 0.9 s | 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