Notation reminder: mass number as a left superscript (e.g., ⁴⁸Ca).
Columns: Isotope | Z | A | Stable? | Half‑life | Decay mode(s) | Daughter | Radiation | Origin | Uses | Notes.
Backbone: half‑lives, branches, and daughters from the evaluated Isotopes of calcium table (NUBASE/ENSDF/AME sourced). Where relevant, I add focused primary sources (e.g., ⁴¹Ca, ⁴⁷Ca/⁴⁷Sc, ⁴⁸Ca). (Wikipedia)
| Isotope | Z | A | Stable? | Half‑life | Decay mode(s) | Daughter | Radiation | Origin | Uses | Notes |
|---|---|---|---|---|---|---|---|---|---|---|
| ³⁵Ca | 20 | 35 | Unstable | 25.7(2) ms | β⁺, p (95.8%); β⁺,2p 4.2%; rare β⁺ | ³⁴Ar; ³³Cl; ³⁵K | β⁺; delayed p/2p | Synthetic | Dripline β⁺p studies | Proton‑rich. (Wikipedia) |
| ³⁶Ca | 20 | 36 | Unstable | 100.9(13) ms | β⁺, p 51.2%; β⁺ 48.8% | ³⁵Ar; ³⁶K | β⁺; delayed p | Synthetic | β⁺p statistics | — (Wikipedia) |
| ³⁷Ca | 20 | 37 | Unstable | 181.0(9) ms | β⁺, p 76.8%; β⁺ 23.2% | ³⁶Ar; ³⁷K | β⁺; delayed p | Synthetic | Reaction/structure | — (Wikipedia) |
| ³⁸Ca | 20 | 38 | Unstable | 443.70(25) ms | β⁺ | ³⁸K | β⁺ | Synthetic | β⁺ standards | — (Wikipedia) |
| ³⁹Ca | 20 | 39 | Unstable | 860.3(8) ms | β⁺ | ³⁹K | β⁺ | Synthetic | β⁺ spectroscopy | — (Wikipedia) |
| ⁴⁰Ca | 20 | 40 | Stable | — | — | — | — | Natural (96.94%) | K–Ca dating (radiogenic ⁴⁰Ca from ⁴⁰K) | Doubly‑magic Z=20,N=20; K–Ca dating revived by modern TIMS/MC‑ICP‑MS. (Wikipedia) |
| ⁴¹Ca | 20 | 41 | Unstable | 9.94(15)×10⁴ y | EC → ⁴¹K | ⁴¹K | X‑rays/Auger (EC) | Cosmogenic (n‑activation of ⁴⁰Ca in soils) & synthetic | Ultra‑long‑lived tracer for bone turnover/osteoporosis and radiometric dating | 3.3 keV X‑rays used in precise t½ work; early dating proposals (AMS). (Wikipedia, journals.uair.arizona.edu, Nature) |
| ⁴²Ca | 20 | 42 | Stable | — | — | — | — | Natural (0.647%) | Stable‑isotope tracers of Ca absorption (dual ⁴²Ca/⁴⁴Ca) | Clinical/nutrition studies. (Journal of Nutrition) |
| ⁴³Ca | 20 | 43 | Stable | — | — | — | — | Natural (0.135%) | Solid‑state ⁴³Ca‑NMR (I = 7/2) for bone/mineral materials | Low sensitivity at natural abundance; advancing methods. (PMC) |
| ⁴⁴Ca | 20 | 44 | Stable | — | — | — | — | Natural (2.09%) | Stable‑isotope tracer (with ⁴²Ca) in human Ca absorption | IRMS/MC‑ICP‑MS workflows. (Journal of Nutrition) |
| ⁴⁵Ca | 20 | 45 | Unstable | 162.61(9) d | β⁻ → ⁴⁵Sc (100%) | ⁴⁵Sc | β⁻ (low‑E) | Synthetic (activation) | Radiotracer in bone/mineral kinetics; autoradiography; historical physiology | Pure β‑emitter; widely used in labs. (Wikipedia, University of Maryland, Baltimore, PMC) |
| ⁴⁶Ca | 20 | 46 | Stable | — | — | — | — | Natural (0.004%) | Enrichment target → ⁴⁷Ca production | Very low abundance; “observationally stable”. (Wikipedia) |
| ⁴⁷Ca | 20 | 47 | Unstable | 4.536(3) d | β⁻ → ⁴⁷Sc | ⁴⁷Sc | β⁻; γ (from ⁴⁷Sc*) | Synthetic (n,γ on ⁴⁶Ca) | Parent in ⁴⁷Ca/⁴⁷Sc generator for theranostics | ⁴⁷Sc (t½ ≈ 3.35 d) β⁻ therapy; generator chemistry active area. (PMC, ScienceDirect, SpringerOpen) |
| ⁴⁸Ca | 20 | 48 | Unstable (quasi‑stable) | 5.6(10)×10¹⁹ y | 2νββ → ⁴⁸Ti | ⁴⁸Ti | 2 β⁻ (+ ν̄) | Natural (0.187%) | Double‑β decay experiments; projectile for superheavy‑element synthesis | Neutron‑rich, “doubly‑magic‑like”; used in ⁴⁸Ca + ²⁴⁹Cf → ²⁹⁴Og campaigns. (Wikipedia, ScienceDirect, Physical Review Links) |
| ⁴⁹Ca | 20 | 49 | Unstable | 8.718(6) min | β⁻ → ⁴⁹Sc | ⁴⁹Sc | β⁻ | Synthetic | β/γ spectroscopy | — (Wikipedia) |
| ⁵⁰Ca | 20 | 50 | Unstable | 13.45(5) s | β⁻ → ⁵⁰Sc | ⁵⁰Sc | β⁻ | Synthetic | Structure | — (Wikipedia) |
| ⁵¹Ca | 20 | 51 | Unstable | 10.0(8) s | β⁻ (± β⁻,n?) | ⁵¹Sc (…⁵⁰Sc) | β⁻; delayed n? | Synthetic | β‑delayed‑n limits | — (Wikipedia) |
| ⁵²Ca | 20 | 52 | Unstable | 4.6(3) s | β⁻ (> 98%); β⁻,n < 2% | ⁵²Sc; ⁵¹Sc | β⁻; delayed n | Synthetic | N=32 subshell closure testbed | N=32 magicity established in Ca region. (Wikipedia, GSI Indico (Indico), CERN Document Server) |
| ⁵³Ca | 20 | 53 | Unstable | 461(90) ms | β⁻ 60%; β⁻,n 40% | ⁵³Sc; ⁵²Sc | β⁻; delayed n | Synthetic | β‑n statistics | — (Wikipedia) |
| ⁵⁴Ca | 20 | 54 | Unstable | 90(6) ms | β⁻ (± β⁻,n/2n?) | ⁵⁴Sc (…⁵³/⁵²Sc) | β⁻; delayed n? | Synthetic | N=34 subshell closure evidence | High E(2⁺) & knockout data support N=34 closure. (PubMed, Physical Review Links) |
| ⁵⁵Ca | 20 | 55 | Unstable | 22(2) ms | β⁻ (± β⁻,n/2n?) | ⁵⁵Sc (…⁵⁴/⁵³Sc) | β⁻; delayed n? | Synthetic | Dripline approach | — (Wikipedia) |
| ⁵⁶Ca | 20 | 56 | Unstable | 11(2) ms | β⁻ (± β⁻,n/2n?) | ⁵⁶Sc (…⁵⁵/⁵⁴Sc) | β⁻; delayed n? | Synthetic | Shell evolution beyond N=34 | — (Wikipedia) |
| ⁵⁷Ca | 20 | 57 | Unstable | ≈ 8 ms (#; > 620 ns) | β⁻? (± n/2n?) | ⁵⁷Sc (…⁵⁶/⁵⁵Sc) | β⁻; delayed n? | Synthetic | Edge‑of‑stability tests | Trend‑evaluated (#). (Wikipedia) |
| ⁵⁸Ca | 20 | 58 | Unstable | ≈ 4 ms (#; > 620 ns) | β⁻? (± n/2n?) | ⁵⁸Sc (…⁵⁷/⁵⁶Sc) | β⁻; delayed n? | Synthetic | Edge‑of‑stability tests | Trend‑evaluated (#). (Wikipedia) |
| ⁵⁹Ca | 20 | 59 | Unstable | ≈ 5 ms (#; > 400 ns) | β⁻? (± n/2n?) | ⁵⁹Sc (…⁵⁸/⁵⁷Sc) | β⁻; delayed n? | Synthetic | Neutron‑rich frontier | Trend‑evaluated (#). (Wikipedia) |
| ⁶⁰Ca | 20 | 60 | Unstable | ≈ 2 ms (#; > 400 ns) | β⁻? (± n/2n?) | ⁶⁰Sc (…⁵⁹/⁵⁸Sc) | β⁻; delayed n? | Synthetic | Heaviest Ca observed (2018) | Discovery at RIKEN; implications for N=40 region. (Physical Review Links, Wikipedia) |
Radiation key: β⁺/EC → positrons/annihilation γ (511 keV) and/or characteristic X‑rays (EC); β⁻ (electron); β⁻,n/2n = β‑decay with 1/2 delayed neutron(s); p/2p = prompt proton(s) from proton‑unbound branches; ββ (2ν) = two‑neutrino double‑β decay.
Applied & structural highlights (Calcium)
- Stable Ca tracers (⁴²Ca, ⁴⁴Ca) underpin dual‑isotope methods for true fractional Ca absorption in nutrition and clinical studies; δ⁴⁴/⁴²Ca in blood/urine acts as a biomarker of bone balance. (Journal of Nutrition, PMC, Kidney International)
- ⁴³Ca (I = 7/2) enables solid‑state NMR of bone/minerals, albeit with low sensitivity at natural abundance (active method development). (PMC)
- ⁴⁵Ca (162.61 d) is a pure β⁻ radiotracer widely used for bone and mineral kinetics and autoradiography. (University of Maryland, Baltimore, PMC)
- ⁴⁷Ca → ⁴⁷Sc forms a practical generator pair for theranostics (β⁻ therapy with ⁴⁷Sc), produced by irradiation of enriched ⁴⁶Ca. (PMC, ScienceDirect)
- ⁴⁸Ca is both a double‑β nucleus (T½ ≈ 5.6×10¹⁹ y) and a favored projectile that enabled synthesis of Og (Z = 118) and other superheavy nuclides. (ScienceDirect, Physical Review Links)
- Neutron‑rich structure: N=32 magicity around ⁵²Ca and N=34 subshell closure at ⁵⁴Ca are now well‑supported; ⁶⁰Ca was discovered in 2018, pushing the chain’s known limit. (GSI Indico (Indico), PubMed, Physical Review Links)
Totals — Calcium (Z = 20)
- Stable5 (⁴⁰Ca, ⁴²Ca, ⁴³Ca, ⁴⁴Ca, ⁴⁶Ca)
- Unstable (radioisotopes)21 (³⁵–³⁹Ca, ⁴¹Ca, ⁴⁵Ca, ⁴⁷–⁶⁰Ca; ⁴⁸Ca is very long‑lived 2νββ)
- Total isotopes26. (Wikipedia)
Running cumulative totals (H → Ca, Z = 1…20)
- Cumulative total isotopes376 (prior through K: 350 • Ca: +26)
- Cumulative stable45 (prior through K: 40 • Ca: +5)
- Cumulative unstable331
Sources & cross‑checks
- Isotopes of calcium — complete per‑nuclide list with half‑lives/branches/daughters; overview of natural abundances and cosmogenic ⁴¹Ca production; discovery note for ⁶⁰Ca. (Wikipedia)
- ⁴¹Ca half‑life & detection (3.3 keV X‑rays) and dating potential: Radiocarbon/AMS studies and classic Nature note. (journals.uair.arizona.edu, Nature)
- ⁴⁷Ca/⁴⁷Sc generator (production routes, half‑lives, separations) — theranostic reviews and process comparisons. (PMC, ScienceDirect)
- ⁴⁸Ca double‑β measurements and role as SHE projectile; Og (118) synthesis with ⁴⁸Ca + ²⁴⁹Cf. (ScienceDirect, Physical Review Links)
- Shell closures (N = 32, 34) in Ca region — mass/knockout/γ‑spectroscopy evidence. (GSI Indico (Indico), PubMed)
- Stable‑isotope/biomedical applications — dual‑tracer nutrition and δ⁴⁴/⁴²Ca biomarker literature; ⁴³Ca‑NMR advances. (Journal of Nutrition, PMC)
Next: Scandium — Sc (Z = 21).
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