Across Earth and in the stars, calcium shows up in everything from shells and bones to meteorites and stellar cores. Its isotopes tell a story about formation, age, and nuclear behavior that researchers and educators often map out for both practical uses and pure curiosity.
There are 26 Calcium Isotopes, ranging from Ca-35 to Ca-60. For each isotope you’ll find below Mass number (A),Half-life (s/yr),Decay mode to make comparisons easier and to highlight which nuclides are stable, long-lived, or short-lived as you scan the list.
Which calcium isotopes are stable and most common in nature?
Natural calcium is dominated by Ca-40, with smaller amounts of Ca-42, Ca-43, Ca-44, Ca-46 and Ca-48 considered stable; Ca-40 accounts for roughly 97% of terrestrial calcium. These stable isotopes are the ones you’ll encounter in geology, biology and materials studies, while the rarer species are used as tracers or for nuclear-structure research.
How are short-lived isotopes like Ca-35 produced and studied?
Short-lived isotopes such as Ca-35 are typically produced in particle accelerators or nuclear reactors via spallation, fragmentation, or proton/neutron reactions, then separated and detected with fast spectroscopy and decay counting; their measured half-lives and decay modes help refine nuclear models and inform astrophysical processes.
Calcium Isotopes
| Isotope | Mass number (A) | Half-life (s/yr) | Decay mode |
|---|---|---|---|
| Ca-35 | 35 | 0.04 s | Proton emission / β+ |
| Ca-36 | 36 | 0.30 s | β+ / electron capture |
| Ca-37 | 37 | 0.18 s | β+ / electron capture |
| Ca-38 | 38 | 0.65 s | β+ / electron capture |
| Ca-39 | 39 | 0.86 s | β+ / electron capture |
| Ca-40 | 40 | stable | Stable |
| Ca-41 | 41 | 103,000 yr | Electron capture |
| Ca-42 | 42 | stable | Stable |
| Ca-43 | 43 | stable | Stable |
| Ca-44 | 44 | stable | Stable |
| Ca-45 | 45 | 14,060,000 s | β− |
| Ca-46 | 46 | stable | Stable |
| Ca-47 | 47 | 392,000 s | β− |
| Ca-48 | 48 | 43,000,000,000,000,000,000 yr | Double β− (very rare) |
| Ca-49 | 49 | 522 s | β− |
| Ca-50 | 50 | 14 s | β− (delayed neutron possible) |
| Ca-51 | 51 | 0.50 s | β− (delayed neutron) |
| Ca-52 | 52 | 4.60 s | β− (delayed neutron) |
| Ca-53 | 53 | 1.60 s | β− (delayed neutron) |
| Ca-54 | 54 | 0.14 s | β− (delayed neutron) |
| Ca-55 | 55 | 0.37 s | β− (delayed neutron) |
| Ca-56 | 56 | 0.08 s | β− (delayed neutron) |
| Ca-57 | 57 | 0.02 s | β− (delayed neutron) |
| Ca-58 | 58 | 0.01 s | β− (delayed neutron) |
| Ca-59 | 59 | 0.002 s | β− (delayed neutron) |
| Ca-60 | 60 | 0.001 s | β− (delayed neutron) |
Images and Descriptions
Ca-35
Very proton-rich, produced in projectile-fragmentation experiments. Decays rapidly by proton emission and β+; not found in nature. Useful for studying nuclear structure near the proton drip line and pairing effects in light nuclei.
Ca-36
Proton-rich synthetic nuclide made in accelerators; decays by β+ and electron capture. No natural occurrence. Studied in nuclear reaction experiments to map shell closures and proton-rich decay pathways.
Ca-37
Short-lived, produced in spallation and fragmentation facilities. Decays by β+ and electron capture to potassium isotopes. Useful for probing mirror nuclei and testing shell-model predictions in light calcium isotopes.
Ca-38
Laboratory-produced proton-rich isotope. Decays by β+ to potassium isotopes and has been used in experiments exploring isospin symmetry and weak interaction strengths in light nuclei.
Ca-39
Synthetic, proton-rich isotope created in fragmentation reactions. Decays by β+ to K-39. Studied for its decay scheme and contributions to understanding nuclear forces near stability.
Ca-40
Most abundant natural calcium isotope (~96.94%). Stable, major constituent of rocks, shells, bones, and widely used in geochemistry and radiogenic studies as a stable reference isotope.
Ca-41
Long-lived radioisotope produced by cosmic rays and neutron activation; half-life ≈103,000 years. Found in trace amounts in nature and used as a tracer in geological dating and low-background studies.
Ca-42
Minor natural isotope (~0.65%). Stable and found in terrestrial materials. Useful in mass-spectrometry studies and for precise isotope ratio measurements in geochemistry and environmental science.
Ca-43
Stable isotope (~0.135% natural abundance). Has nonzero nuclear spin, making it useful for NMR studies and nuclear structure investigations in calcium-containing materials.
Ca-44
Stable (~2.09% abundance) and common in nature. Used in isotope geochemistry and as a calibration isotope in mass spectrometry; contributes to studies of nucleosynthesis.
Ca-45
Radioactive with half-life ≈162.7 days (14,060,000 s). Produced in reactors and accelerators; used as a tracer in biological calcium uptake studies and biomedical research due to its measurable β− emissions.
Ca-46
Minor natural isotope (~0.004% abundance). Stable and used in high-precision isotope ratio work; often cited in studies of nucleosynthesis and as a reference in mass spectrometry.
Ca-47
Radioactive (≈4.54 days, 392,000 s). Produced by neutron capture and accelerator reactions; decays by β− to scandium-47. Useful in nuclear structure studies and as a calibration source in experiments.
Ca-48
Very neutron-rich, trace natural abundance (~0.187%). Undergoes rare double β− decay with an extremely long half-life (~4.3×10^19 years). Important for double-beta decay research and nuclear structure studies.
Ca-49
Neutron-rich isotope produced by fragmentation; half-life ~8.7 minutes (522 s). Decays by β− and used to study shell evolution and neutron-rich nuclear behavior near N=28–30.
Ca-50
Neutron-rich, short-lived (≈14 s), synthesized in fragmentation. Decays by β−, possibly with delayed neutron emission; studied to probe shell closures and neutron excess effects.
Ca-51
Very short-lived, produced in high-energy fragmentation. Decays by β− with possible delayed neutron emission. Used experimentally to map decay properties toward the neutron drip line.
Ca-52
Neutron-rich isotope with half-life ≈4.6 s. Produced in radioactive-beam facilities; shows β− decay often accompanied by delayed neutrons. Important for understanding neutron-rich shell evolution.
Ca-53
Short-lived, generated in lab fragmentation; decays by β− with delayed neutron emission. Studied for nuclear structure beyond the N=28 shell and for r-process modeling inputs.
Ca-54
Very neutron-rich, half-life ≈0.14 s. Created in projectile-fragmentation experiments and decays rapidly by β− with neutron emission; useful for extreme neutron-rich nuclear physics.
Ca-55
Extremely neutron-rich, short half-life (~0.37 s). Observed in fragmentation studies and decays by β− with delayed neutrons. Helps map limits of nuclear binding for calcium isotopes.
Ca-56
Very short-lived (~0.08 s), produced only in high-energy facilities. Decays by β− and emits delayed neutrons; informs models of neutron-rich matter and shell behavior.
Ca-57
Observed in fragmentation experiments with a very short half-life (~0.02 s). Decays by β− with neutron emission; significant for studies of the neutron drip line.
Ca-58
Extremely short-lived (~0.01 s), produced in specialized radioactive-beam experiments. Decays by rapid β− emission with neutrons; notable for probing extreme neutron-to-proton ratios.
Ca-59
Transient nuclide observed in very neutron-rich fragmentation studies (~2 ms). Decays almost immediately by β− and neutron emission; used to explore the limits of nuclear stability.
Ca-60
Heaviest observed calcium isotope to date, extremely short-lived (~1 ms). Produced in cutting-edge experiments; decay by β− with neutron emission helps define the neutron drip line for calcium.
