ChemWhiz ReferenceNuclear Chemistry
Half-Lives of Radioactive Isotopes
Half-lives or experimental limits, decay modes, and applications or research relevance for 61 isotopes. A lower limit is identified explicitly when decay has not been observed. For observed first-order radioactive decay, t½ = ln 2 / k and after n half-lives the remaining fraction is (1/2)n.
01Use this when
First-order decay math (N = N0(1/2)n after n = t/t½ half-lives) and radiometric dating.
02Conditions
Half-life is constant: independent of temperature, pressure, and chemical form.
03Watch out
Match the half-life units to the elapsed-time units before taking the ratio.
Half-Lives and Decay Modes
Use the half-life with first-order decay to find the fraction remaining after time t, and for radiometric dating.
61 of 61
| 14C | Carbon-14 | 6 | 5730 y | β- | Radiocarbon dating of once-living material |
| 13N | Nitrogen-13 | 7 | 9.97 m | β+ | Myocardial perfusion PET imaging using nitrogen-13 ammonia |
| 15F | Fluorine-15 | 9 | 4.1 × 10-22 s | p | Nuclear-data research: p decay and half-life characterization |
| 18F | Fluorine-18 | 9 | 110 m | β+ | PET scans |
| 24Na | Sodium-24 | 11 | 15.00 h | β- | Radiotracer leak detection in heat exchangers |
| 32P | Phosphorus-32 | 15 | 14.29 d | β- | Radiotracer studies of phosphorus uptake and cycling |
| 40K | Potassium-40 | 19 | 1.27 × 109 y | β or E.C. | Potassium-argon radiometric dating of rocks |
| 49Fe | Iron-49 | 26 | 0.08 s | β+ | Nuclear-data research: β+ decay and half-life characterization |
| 60Fe | Iron-60 | 26 | 2.6 × 106 y | β- | Nuclear-data research: β- decay and half-life characterization |
| 60Co | Cobalt-60 | 27 | 5.27 y | β- | cancer treatment |
| 87Rb | Rubidium-87 | 37 | 4.7 × 1010 y | β- | Rubidium-strontium radiometric dating of rocks |
| 90Sr | Strontium-90 | 38 | 29 y | β- | Nuclear-data research: β- decay and half-life characterization |
| 99mTc | Technetium-99m * | 43 | 6.01 h | γ | scans of brain, lung, heart, bone |
| 115In | Indium-115 * | 49 | 4.41 × 1014 y | β- | Nuclear-data research: β- decay and half-life characterization |
| 131I | Iodine-131 | 53 | 8.040 d | β- | thyroid scans and treatment |
| 142Ce | Cerium-142 * | 58 | > 5 × 1016 y (limit) | No decay observed | Research on nuclear stability and searches for unobserved decay |
| 201Tl | Thallium-201 | 81 | 73 h | E.C. | heart and arteries scans; cardiac stress tests |
| 208Tl | Thallium-208 | 81 | 3.07 m | β- | Nuclear-data research: β- decay and half-life characterization |
| 210Pb | Lead-210 | 82 | 22.3 y | β- | Dating sediment cores and measuring accumulation rates |
| 212Pb | Lead-212 | 82 | 10.6 h | β- | Nuclear-data research: β- decay and half-life characterization |
| 214Pb | Lead-214 | 82 | 26.8 m | β- | Nuclear-data research: β- decay and half-life characterization |
| 206Bi | Bismuth-206 | 83 | 6.243 d | E.C. | Nuclear-data research: E.C. decay and half-life characterization |
| 210Bi | Bismuth-210 | 83 | 5.01 d | β- | Nuclear-data research: β- decay and half-life characterization |
| 212Bi | Bismuth-212 | 83 | 60.55 m | α or β- | Nuclear-data research: α or β- decay and half-life characterization |
| 210Po | Polonium-210 | 84 | 138.4 d | α | Static eliminators and ion generators |
| 212Po | Polonium-212 | 84 | 3 × 10-7 s | α | Nuclear-data research: α decay and half-life characterization |
| 216Po | Polonium-216 | 84 | 0.15 s | α | Nuclear-data research: α decay and half-life characterization |
| 218Po | Polonium-218 | 84 | 3.05 m | α | Nuclear-data research: α decay and half-life characterization |
| 215At | Astatine-215 | 85 | 1.0 × 10-4 s | α | Nuclear-data research: α decay and half-life characterization |
| 218At | Astatine-218 | 85 | 1.6 s | α | Nuclear-data research: α decay and half-life characterization |
| 220Rn | Radon-220 | 86 | 55.6 s | α | Nuclear-data research: α decay and half-life characterization |
| 222Rn | Radon-222 | 86 | 3.82 d | α | Nuclear-data research: α decay and half-life characterization |
| 224Ra | Radium-224 | 88 | 3.66 d | α | Nuclear-data research: α decay and half-life characterization |
| 226Ra | Radium-226 | 88 | 1600 y | α | Nuclear-data research: α decay and half-life characterization |
| 228Ra | Radium-228 | 88 | 5.75 y | β- | Nuclear-data research: β- decay and half-life characterization |
| 228Ac | Actinium-228 | 89 | 6.13 h | β- | Nuclear-data research: β- decay and half-life characterization |
| 228Th | Thorium-228 | 90 | 1.913 y | α | Nuclear-data research: α decay and half-life characterization |
| 232Th | Thorium-232 | 90 | 1.4 × 1010 y | α | Fertile material for producing uranium-233 in fuel-cycle research |
| 233Th | Thorium-233 | 90 | 22 m | β- | Nuclear-data research: β- decay and half-life characterization |
| 234Th | Thorium-234 | 90 | 24.10 d | β- | Nuclear-data research: β- decay and half-life characterization |
| 233Pa | Protactinium-233 | 91 | 27 d | β- | Nuclear-data research: β- decay and half-life characterization |
| 233U | Uranium-233 | 92 | 1.59 × 105 y | α | Fissile material studied for nuclear fuel cycles |
| 234U | Uranium-234 | 92 | 2.45 × 105 y | α | Nuclear-data research: α decay and half-life characterization |
| 235U | Uranium-235 | 92 | 7.03 × 108 y | α | Fissile material in nuclear reactor fuel |
| 238U | Uranium-238 | 92 | 4.47 × 109 y | α | Uranium-lead radiometric dating; fertile material for plutonium production |
| 239U | Uranium-239 | 92 | 23.54 m | β- | Nuclear-data research: β- decay and half-life characterization |
| 239Np | Neptunium-239 | 93 | 2.3 d | β- | Nuclear-data research: β- decay and half-life characterization |
| 239Pu | Plutonium-239 | 94 | 2.407 × 104 y | α | Fissile material in nuclear fuel |
| 240Pu | Plutonium-240 * | 94 | 6.54 × 103 y | α | Nuclear-data research: α decay and half-life characterization |
| 241Pu | Plutonium-241 | 94 | 14.4 y | α or β- | Nuclear-data research: α or β- decay and half-life characterization |
| 241Am | Americium-241 | 95 | 432.2 y | α | Ionization smoke detectors |
| 242Cm | Curium-242 | 96 | 162.8 d | α | Nuclear-data research: α decay and half-life characterization |
| 243Bk | Berkelium-243 | 97 | 4.5 h | α or E.C. | Nuclear-data research: α or E.C. decay and half-life characterization |
| 253Es | Einsteinium-253 | 99 | 20.47 d | α | Nuclear-data research: α decay and half-life characterization |
| 254Fm | Fermium-254 | 100 | 3.24 h | α or S.F. | Nuclear-data research: α or S.F. decay and half-life characterization |
| 255Fm | Fermium-255 | 100 | 20.1 h | α | Nuclear-data research: α decay and half-life characterization |
| 256Md | Mendelevium-256 | 101 | 76 m | α or E.C. | Nuclear-data research: α or E.C. decay and half-life characterization |
| 254No | Nobelium-254 | 102 | 55 s | α | Nuclear-data research: α decay and half-life characterization |
| 257Lr | Lawrencium-257 | 103 | 0.65 s | α | Nuclear-data research: α decay and half-life characterization |
| 260Db | Dubnium-260 * | 105 | 1.5 s | α or S.F. | Nuclear-data research: α or S.F. decay and half-life characterization |
| 263Sg | Seaborgium-263 | 106 | 0.8 s | α or S.F. | Nuclear-data research: α or S.F. decay and half-life characterization |
Important Notes
- Half-life units: y = years, d = days, h = hours, m = minutes, s = seconds. Emission codes: E.C. = electron capture, S.F. = spontaneous fission.
- Decay is first-order: after n = t/t½ half-lives, N = N0(1/2)n; and t½ = ln 2 / k regardless of the starting amount.
- Dating windows follow the half-life: carbon-14 (5730 y) dates once-living material to about 50,000 years; uranium-238 (4.47 × 109 y) dates rocks on geologic timescales.
- Technetium-99m is a METASTABLE nuclear state (the m) of technetium-99, the workhorse of diagnostic imaging, reached from molybdenum-99 generators.
- Starred rows are curated corrections of published-table misprints. Dubnium-260 is listed under its pre-1997 name hahnium (Ha).
- Plutonium-240 is mislabeled as a second plutonium-239; its 6.54 × 103 y half-life identifies it as Pu-240.
- Technetium-99m is 6.01 h (the IAEA value); older tables list 8.01 h.
- Indium-115 is (4.41 ± 0.25) × 1014 y; the older source table gives an incorrect 5.1 × 1015 y. Cerium-142 has no observed decay: > 5 × 1016 y is an evaluated experimental lower limit, not a measured half-life or a prediction.
- Applications are selected examples, not an exhaustive catalogue. Nuclear-data research identifies studied decay properties and does not imply a commercial, medical or industrial application, or absence of other uses.
- This table is a general reference.
Verification references: OpenStax Chemistry 2e, Appendix M (Half-Lives for Several Radioactive Isotopes); IAEA Live Chart of Nuclides (ChemWhiz corrections and supplemental medical isotopes); IAEA Radiation Technology Series No. 2, section 4.3: radiocarbon dating; USGS Geologic Time: Radiometric Time Scale; DailyMed Ammonia N-13 prescribing information; NRC NUREG/CR-1156: Am-241 smoke detectors; NRC Science 101: What is Plutonium?; IAEA TECDOC 1805: phosphorus radiotracer studies; IAEA Training Course Series 38: Leak Detection in Heat Exchangers; IAEA Bulletin 35(2), 1993: nuclear and isotopic techniques; NRC NUREG-1717, section 4.1: Static Eliminators and Ion Generators; NRC glossary: fissile material and fertile material.