Notation: mass number as a left superscript (e.g., ⁵¹Cr).
Columns: Isotope | Z | A | Stable? | Half‑life | Decay mode(s) | Daughter | Radiation | Origin | Uses | Notes.
Backbone: evaluated NUBASE/ENSDF values as compiled in Isotopes of chromium; LiveChart/NuDat consulted. Applied notes for ⁵¹Cr (320 keV γ; RBC/GFR tests) and isotope‑geochemistry context included. (Wikipedia, IAEA Nuclear Data Services, nndc.bnl.gov)
| Isotope | Z | A | Stable? | Half‑life | Decay mode(s) | Daughter | Radiation | Origin | Uses | Notes |
|---|---|---|---|---|---|---|---|---|---|---|
| ⁴²Cr | 24 | 42 | No | 13.3(10) ms | β⁺ 94.4%; β⁺p 5.6% | ⁴²V; ⁴¹Ti | β⁺; delayed p; 511 keV γ | Synthetic | Dripline research | — (Wikipedia) |
| ⁴³Cr | 24 | 43 | No | 21.1(3) ms | β⁺p 79.3%; β⁺2p 11.6%; β⁺ 8.97%; β⁺3p 0.13% | ⁴²Ti; ⁴¹Sc; ⁴³V; ⁴⁰Ca | β⁺; delayed p/2p/3p | Synthetic | Multi‑p emission studies | — (Wikipedia) |
| ⁴⁴Cr | 24 | 44 | No | 42.8(6) ms | β⁺ 88%; β⁺p 12% | ⁴⁴V; ⁴³Ti | β⁺; delayed p | Synthetic | Structure/decay | — (Wikipedia) |
| ⁴⁵Cr | 24 | 45 | No | 60.9(4) ms | β⁺ 65.6%; β⁺p 34.4% | ⁴⁵V; ⁴⁴Ti | β⁺; delayed p | Synthetic | β⁺p statistics | ⁴⁵ᵐCr: 107 keV, > 80 µs (IT). (Wikipedia) |
| ⁴⁶Cr | 24 | 46 | No | 224.3(13) ms | β⁺ | ⁴⁶V | β⁺ | Synthetic | Reaction studies | — (Wikipedia) |
| ⁴⁷Cr | 24 | 47 | No | 461.6(15) ms | β⁺ | ⁴⁷V | β⁺ | Synthetic | Decay spectroscopy | — (Wikipedia) |
| ⁴⁸Cr | 24 | 48 | No | 21.56(3) h | β⁺ | ⁴⁸V | β⁺ | Synthetic | Research (medium‑lived β⁺) | — (Wikipedia) |
| ⁴⁹Cr | 24 | 49 | No | 42.3(1) min | β⁺ | ⁴⁹V | β⁺ | Synthetic | β⁺ spectroscopy | — (Wikipedia) |
| ⁵⁰Cr | 24 | 50 | Observationally stable | — | — (2β⁺ to ⁵⁰Ti constrained) | — | — | Natural (4.345%) | Standards; isotope geochemistry | 2β⁺ suspected; t½ > 1.3×10¹⁸ y limit. (Wikipedia) |
| ⁵¹Cr | 24 | 51 | No (natural trace, synthetic) | 27.7015(11) d | EC → ⁵¹V | ⁵¹V | γ 320.08 keV (~10%); X‑rays (EC) | Neutron‑activation of ⁵⁰Cr | Medical tracer: RBC mass/survival; GI‑bleed localization; GFR tests | Standard 27.7 d EC; 320 keV γ used clinically/industrially. (Wikipedia, IAEA Nuclear Data Services, hpschapters.org) |
| ⁵²Cr | 24 | 52 | Stable | — | — | — | — | Natural (83.789%) | Stable‑isotope geochemistry (δ⁵³Cr/δ⁵²Cr) | Reference isotope in Cr IRMS. (Wikipedia) |
| ⁵³Cr | 24 | 53 | Stable | — | — | — | — | Natural (9.501%) | Radiogenic daughter of ⁵³Mn; cosmochemistry; redox proxy in sediments | Mn–Cr chronometer; seawater‑oxygen proxy. (Wikipedia) |
| ⁵⁴Cr | 24 | 54 | Stable | — | — | — | — | Natural (2.365%) | Cosmochemistry (nucleosynthetic ε⁵⁴Cr anomalies) | Stable. (Wikipedia) |
| ⁵⁵Cr | 24 | 55 | No | 3.497(3) min | β⁻ | ⁵⁵Mn | β⁻ | Synthetic | Activation/β− studies | — (Wikipedia) |
| ⁵⁶Cr | 24 | 56 | No | 5.94(10) min | β⁻ | ⁵⁶Mn | β⁻ | Synthetic | Activation/β− studies | — (Wikipedia) |
| ⁵⁷Cr | 24 | 57 | No | 21.1(10) s | β⁻ | ⁵⁷Mn | β⁻ | Synthetic | Decay schemes | — (Wikipedia) |
| ⁵⁸Cr | 24 | 58 | No | 7.0(3) s | β⁻ | ⁵⁸Mn | β⁻ | Synthetic | β− spectroscopy | — (Wikipedia) |
| ⁵⁹Cr | 24 | 59 | No | 1.05(9) s | β⁻ | ⁵⁹Mn | β⁻ | Synthetic | β− spectroscopy | ⁵⁹ᵐCr: 502.7 keV, 96(20) µs (IT). (Wikipedia) |
| ⁶⁰Cr | 24 | 60 | No | 490(10) ms | β⁻ | ⁶⁰Mn | β⁻ | Synthetic | Structure (N≈36) | — (Wikipedia) |
| ⁶¹Cr | 24 | 61 | No | 243(9) ms | β⁻ | ⁶¹Mn | β⁻ | Synthetic | Neutron‑rich decay | — (Wikipedia) |
| ⁶²Cr | 24 | 62 | No | 206(12) ms | β⁻ | ⁶²Mn | β⁻ | Synthetic | β− decay mapping | — (Wikipedia) |
| ⁶³Cr | 24 | 63 | No | 129(2) ms | β⁻ | ⁶³Mn | β⁻ | Synthetic | β− decay mapping | — (Wikipedia) |
| ⁶⁴Cr | 24 | 64 | No | 43(1) ms | β⁻ | ⁶⁴Mn | β⁻ | Synthetic | Dripline approach | — (Wikipedia) |
| ⁶⁵Cr | 24 | 65 | No | 27.5(21) ms | β⁻ | ⁶⁵Mn | β⁻ | Synthetic | Edge‑of‑stability tests | Value partly trend‑based (#). (Wikipedia) |
| ⁶⁶Cr | 24 | 66 | No | 23.8(18) ms | β⁻ | ⁶⁶Mn | β⁻ | Synthetic | Edge‑of‑stability tests | Value partly trend‑based (#). (Wikipedia) |
| ⁶⁷Cr | 24 | 67 | No | ≈ 11 ms (># 300 ns) | β⁻ ? | ⁶⁷Mn | β⁻ (expected) | Synthetic | Neutron‑rich frontier | Trend‑evaluated (#). (Wikipedia) |
| ⁶⁸Cr | 24 | 68 | No | ≈ 10 ms (># 620 ns) | β⁻ ? | ⁶⁸Mn | β⁻ (expected) | Synthetic | Neutron‑rich frontier | Trend‑evaluated (#). (Wikipedia) |
| ⁶⁹Cr | 24 | 69 | No | ≈ 6 ms (># 620 ns) | β⁻ ? | ⁶⁹Mn | β⁻ (expected) | Synthetic | Heaviest‑odd A listed | Trend‑evaluated (#). (Wikipedia) |
| ⁷⁰Cr | 24 | 70 | No | ≈ 6 ms (># 620 ns) | β⁻ ? | ⁷⁰Mn | β⁻ (expected) | Synthetic | Most neutron‑rich Cr | Trend‑evaluated (#). (Wikipedia) |
Radiation key: β⁺/EC → positron(s) + annihilation γ at 511 keV and/or characteristic X‑rays (for EC); β⁻ (electron); β⁺p/2p/3p = β⁺ followed by delayed proton(s); IT = isomeric transition γ.
Applied highlights: ⁵¹Cr (27.7 d, EC → ⁵¹V, γ 320 keV) is a classic medical tracer for RBC mass/survival, GI‑bleed localization, and GFR determination; Cr stable‑isotope ratios (especially ⁵³Cr/⁵²Cr) are used as redox and paleo‑oxygenation proxies and in Mn–Cr chronometry (⁵³Mn → ⁵³Cr) for early Solar‑System history. (Wikipedia, IAEA Nuclear Data Services)
Totals — Chromium (Z = 24)
- Stable: 4 (⁵⁰Cr, ⁵²Cr, ⁵³Cr, ⁵⁴Cr)
- Unstable (radioisotopes): 25 (⁴²–⁴⁹Cr, ⁵¹Cr, ⁵⁵–⁷⁰Cr; several trend‑evaluated # entries)
- Total isotopes (ground states): 29. (Wikipedia)
Running cumulative totals (H → Cr, Z = 1…24)
- Cumulative total isotopes: 482 (prior through V: 453 • Cr: +29)
- Cumulative stable: 56 (prior through V: 52 • Cr: +4)
- Cumulative unstable: 426
Sources & cross‑checks
- Isotopes of chromium — complete per‑nuclide table (A = 42–70), half‑lives, branches/daughters; cosmochemical context for ⁵³Cr and stable abundances. (Wikipedia)
- IAEA LiveChart of Nuclides (ENSDF backbone) and NNDC NuDat 3 — authoritative decay datasets and definitions; used for verification and γ‑line lookups. (IAEA Nuclear Data Services, nndc.bnl.gov)
- ⁵¹Cr medical/γ data: IAEA medical production card ⁵¹V(p,n)⁵¹Cr (t½ = 27.701 d; γ 320.08 keV) and health‑physics datasheet (clinical use; X‑ray/Auger lines). (IAEA Nuclear Data Services, hpschapters.org)
Next: Manganese — Mn (Z = 25).