Element 42 — Molybdenum (Mo) — Z = 42

Notation: mass number shown as a left superscript (e.g., ⁹⁹Mo).
Columns: Isotope | Z | A | Stable? | Half‑life | Decay mode(s) | Daughter | Radiation | Origin | Uses | Notes.
Backbone: per‑nuclide half‑lives/branches/daughters from the evaluated Isotopes of molybdenum table; natural composition from CIAAW. Key applications: ⁹⁹Mo → ⁹⁹ᵐTc generators (nuclear medicine), ¹⁰⁰Mo double‑beta decay experiments, ⁹⁵/⁹⁷Mo NMR, and the revised ⁹³Mo half‑life. (Wikipedia, ciaaw.org, IAEA Publications, International Atomic Energy Agency, NCBI, arXiv, Nature)

IsotopeZAStable?Half‑lifeDecay mode(s)DaughterRadiationOriginUsesNotes
⁸¹Mo4281No~1 ms (#; > 400 ns)β⁺?; β⁺,p?⁸¹Nb; ⁸⁰Zrβ⁺; pSynthetic (p‑rich)Dripline mappingTrend‑based eval (#). (Wikipedia)
⁸²Mo4282No~30 ms (#; > 400 ns)β⁺?; β⁺,p?⁸²Nb; ⁸¹Zrβ⁺; pSyntheticDriplineTrend‑based (#). (Wikipedia)
⁸³Mo4283No23(19) msβ⁺; β⁺,p?⁸³Nb; ⁸²Zrβ⁺; pSyntheticTentative p‑branch. (Wikipedia)
⁸⁴Mo4284No2.3(3) sβ⁺; β⁺,p?⁸⁴Nb; ⁸³Zrβ⁺; pSynthetic— (Wikipedia)
⁸⁵Mo4285No3.2(2) sβ⁺ 99.86%; β⁺,p 0.14%⁸⁵Nb; ⁸⁴Zrβ⁺; delayed pSynthetic— (Wikipedia)
⁸⁶Mo4286No19.1(3) sβ⁺⁸⁶Nbβ⁺Synthetic— (Wikipedia)
⁸⁷Mo4287No14.1(3) sβ⁺ 85%; β⁺,p 15%⁸⁷Nb; ⁸⁶Zrβ⁺; delayed pSynthetic— (Wikipedia)
⁸⁸Mo4288No8.0(2) minβ⁺⁸⁸Nbβ⁺Synthetic— (Wikipedia)
⁸⁹Mo4289No2.11(10) minβ⁺⁸⁹Nbβ⁺SyntheticIsomer ⁸⁹ᵐMo 190 ms (IT). (Wikipedia)
⁹⁰Mo4290No5.56(9) hβ⁺⁹⁰Nbβ⁺ActivationLab sourceIsomer ⁹⁰ᵐMo 1.14 µs (IT). (Wikipedia)
⁹¹Mo4291No15.49(1) minβ⁺⁹¹Nbβ⁺ActivationIsomer ⁹¹ᵐMo 64.6 s (IT 50%). (Wikipedia)
⁹²Mo4292StableNatural (≈ 0.1465)Targets/standardsOften marked “observationally stable.” (Wikipedia)
⁹³Mo4293No (long‑lived)4839(63) yEC 95.7% → ⁹³ᵐNb (16.1 y, IT); EC 4.3% → ⁹³Nb⁹³ᵐ/⁹³NbX‑rays/AugerActivation/cosmogenicActivation chronometryDirect half‑life determination (2021). (Wikipedia, Nature)
⁹⁴Mo4294StableNatural (≈ 0.0919)Standards; geochem— (Wikipedia)
⁹⁵Mo4295StableNatural (≈ 0.1587)Mo‑NMR nucleusI = 5/2; common NMR target. (Wikipedia, chem.ch.huji.ac.il, ScienceDirect)
⁹⁶Mo4296StableNatural (≈ 0.1667)Standards— (Wikipedia)
⁹⁷Mo4297StableNatural (≈ 0.0958)Mo‑NMR nucleusI = 5/2; lower sensitivity than ⁹⁵Mo. (Wikipedia, chem.ch.huji.ac.il)
⁹⁸Mo4298StableNatural (≈ 0.2429)StandardsOften tagged “observationally stable.” (Wikipedia)
⁹⁹Mo4299No65.932(5) h (~66 h)β⁻ → ⁹⁹ᵐTc (≈ 88.6%); β⁻ → ⁹⁹Tc (≈ 11.4%)⁹⁹ᵐTc/⁹⁹Tcβ⁻; γ (via ⁹⁹ᵐTc, 140 keV)Fission product; LEU/HEU or (n,γ)Parent of ⁹⁹ᵐTc generators used in ≈ 80% of diagnostic nuclear medicineIAEA/NRC overviews. (IAEA Publications, International Atomic Energy Agency, NCBI)
¹⁰⁰Mo42100No (radio‑primordial)7.07(14)×10¹⁸ y (2νββ)2β⁻ → ¹⁰⁰Ru¹⁰⁰Ru2e⁻ + ν̄ₑν̄ₑNatural (≈ 0.0974)Double‑β experiments (NEMO‑3, CUPID‑Mo)NEMO‑3 T½ = 6.81×10¹⁸ y (full dataset). (Wikipedia, arXiv)
¹⁰¹Mo42101No14.61(3) minβ⁻ → ¹⁰¹Tc¹⁰¹Tcβ⁻Activation/fission— (Wikipedia)
¹⁰²Mo42102No11.3(2) minβ⁻ → ¹⁰²Tc¹⁰²Tcβ⁻Activation/fission— (Wikipedia)
¹⁰³Mo42103No67.5(15) sβ⁻ → ¹⁰³Tc¹⁰³Tcβ⁻Fission— (Wikipedia)
¹⁰⁴Mo42104No60(2) sβ⁻ → ¹⁰⁴Tc¹⁰⁴Tcβ⁻Fission— (Wikipedia)
¹⁰⁵Mo42105No36.3(8) sβ⁻ → ¹⁰⁵Tc¹⁰⁵Tcβ⁻Fission— (Wikipedia)
¹⁰⁶Mo42106No8.73(12) sβ⁻ → ¹⁰⁶Tc¹⁰⁶Tcβ⁻Fission— (Wikipedia)
¹⁰⁷Mo42107No3.5(5) sβ⁻ → ¹⁰⁷Tc¹⁰⁷Tcβ⁻FissionIsomer 65.4 keV, 445 ns (IT). (Wikipedia)
¹⁰⁸Mo42108No1.105(10) sβ⁻ > 99.5% → ¹⁰⁸Tc; β⁻, n < 0.5% → ¹⁰⁷Tc¹⁰⁸/¹⁰⁷Tcβ⁻; delayed nFission— (Wikipedia)
¹⁰⁹Mo42109No700(14) msβ⁻ 98.7% → ¹⁰⁹Tc; β⁻, n 1.3% → ¹⁰⁸Tc¹⁰⁹/¹⁰⁸Tcβ⁻; delayed nFissionIsomer 69.7 keV, 210 ns. (Wikipedia)
¹¹⁰Mo42110No292(7) msβ⁻ 98.0% → ¹¹⁰Tc; β⁻, n 2.0% → ¹⁰⁹Tc¹¹⁰/¹⁰⁹Tcβ⁻; delayed nFission— (Wikipedia)
¹¹¹Mo42111No193.6(44) msβ⁻ > 88%; β⁻, n < 12%¹¹¹/¹¹⁰Tcβ⁻; delayed nFissionIsomer ~200 ms (#). (Wikipedia)
¹¹²Mo42112No125(5) msβ⁻; β⁻,n?¹¹²/¹¹¹Tcβ⁻; delayed n?Fission (in‑flight)Trend‑based in parts (#). (Wikipedia)
¹¹³Mo42113No80(2) msβ⁻; β⁻,n?¹¹³/¹¹²Tcβ⁻; delayed n?Fission (in‑flight)Trend‑based (#). (Wikipedia)
¹¹⁴Mo42114No58(2) msβ⁻; β⁻,n?¹¹⁴/¹¹³Tcβ⁻; delayed n?Fission (in‑flight)Independent eval cites 58 ms. (chemlin.org)
¹¹⁵Mo42115No45.5(20) msβ⁻; β⁻,n?; β⁻,2n?¹¹⁵/¹¹⁴/¹¹³Tcβ⁻; delayed n/2nFission (in‑flight)Per evaluated table (recent). (Wikipedia)
¹¹⁶Mo42116No32(4) msβ⁻; β⁻,n?; β⁻,2n?¹¹⁶/¹¹⁵/¹¹⁴Tcβ⁻; delayed n/2nFission (in‑flight)— (Wikipedia)
¹¹⁷Mo42117No22(5) msβ⁻; β⁻,n?; β⁻,2n?¹¹⁷/¹¹⁶/¹¹⁵Tcβ⁻; delayed n/2nFission (in‑flight)— (Wikipedia)
¹¹⁸Mo42118No21(6) msβ⁻; β⁻,n?; β⁻,2n?¹¹⁸/¹¹⁷/¹¹⁶Tcβ⁻; delayed n/2nFission (in‑flight)— (Wikipedia)
¹¹⁹Mo42119No (very uncertain)~12 ms (#; > 550 ns)β⁻?; β⁻,n?; β⁻,2n?¹¹⁹/¹¹⁸/¹¹⁷Tcβ⁻; delayed n?Fission (in‑flight)Frontier regionTrend‑based (#). (Wikipedia)

Radiation key: **β⁺/**EC → positrons (annihilation 511 keV) and/or characteristic X‑rays/Auger (for EC); β⁻ (electron); β⁻, n/2n = β‑decay with delayed neutron(s); p/β⁺,p = (β⁺‑delayed) proton(s); IT = isomeric transition γ.
Natural Mo isotopes & abundances: ⁹²Mo ≈ 14.649%, ⁹⁴Mo ≈ 9.187%, ⁹⁵Mo ≈ 15.873%, ⁹⁶Mo ≈ 16.673%, ⁹⁷Mo ≈ 9.582%, ⁹⁸Mo ≈ 24.292%, ¹⁰⁰Mo ≈ 9.744% (amount fractions; ⁹⁸Mo and ⁹²Mo are “observation‑stable”). (Wikipedia)


Applied & research highlights (Molybdenum)

  • ⁹⁹Mo → ⁹⁹ᵐTc (t½ ≈ 66 h → 6 h): the workhorse generator for diagnostic nuclear medicine. ≈ 88.6% of ⁹⁹Mo decays feed ⁹⁹ᵐTc (140 keV γ), eluted from alumina columns as pertechnetate; production routes include fission (LEU/HEU) and neutron‑capture. (IAEA Publications, International Atomic Energy Agency, NCBI)
  • ¹⁰⁰Mo (2νββ): a radio‑primordial nuclide supporting double‑beta physics; compilations adopt ~7.07×10¹⁸ y, while NEMO‑3 reports (6.81+0.38/−0.40)×10¹⁸ y to ¹⁰⁰Ru. (Wikipedia, arXiv)
  • ⁹⁵Mo & ⁹⁷Mo (I = 5/2): the NMR‑active molybdenum isotopes; ⁹⁵Mo is typically preferred for sensitivity and line‑shape. (chem.ch.huji.ac.il, ScienceDirect)
  • ⁹³Mo (EC, 4.84 ky): recent direct half‑life measurement refined decay to ⁹³ᵐNb (dominant), improving activation dosimetry/chronometry. (Nature)
  • ⁹²Mo & ⁹⁴Mo: p‑process (proton‑rich) p‑nuclides of astrophysical interest in γ‑process modeling. (Wikipedia, thomasrauscher.ch)

Totals — Molybdenum (Z = 42)

  • Stable: 6  (⁹²Mo, ⁹⁴Mo, ⁹⁵Mo, ⁹⁶Mo, ⁹⁷Mo, ⁹⁸Mo).
  • Unstable (radioisotopes, ground states): 33  (⁸¹–⁹¹Mo, ⁹³, ⁹⁹–¹¹⁹Mo; ¹⁰⁰Mo is radio‑primordial 2νββ).
  • Total isotopes (ground states): 39. (Wikipedia)

Running cumulative totals (H → Mo, Z = 1…42)

From the previous step (through Nb) we had ≥ 1028 total (106 stable, ≥ 922 unstable). Adding molybdenum (39 total; 6 stable; 33 unstable) gives:

  • Cumulative total: ≥ 1067
  • Cumulative stable: 112
  • Cumulative unstable: ≥ 955

Sources & cross‑checks

  • Isotopes of molybdenum — authoritative per‑nuclide list (A = 81–119), half‑lives, modes/branches, daughters, and “trend‑based” near‑dripline annotations. Also provides the natural mole fractions listed above. (Wikipedia)
  • CIAAW (IUPAC) — molybdenum isotopic composition background and standard atomic weight (A_r = 95.95). (ciaaw.org)
  • ⁹⁹Mo/⁹⁹ᵐTc generators: production and decay parameters (t½≈66 h; ~88.6% to ⁹⁹ᵐTc) and generator operation (alumina columns, saline elution). (IAEA Publications, International Atomic Energy Agency, NCBI)
  • ¹⁰⁰Mo double‑β: evaluated value (table) and NEMO‑3 measurement. (Wikipedia, arXiv)
  • ⁹³Mo half‑life (4.839 ky): direct determination with improved precision and branching to ⁹³ᵐNb. (Nature)
  • Far n‑rich (¹¹⁴–¹¹⁹Mo): evaluated rows and independent confirmations (e.g., ¹¹⁴Mo t½≈58 ms). (Wikipedia, chemlin.org)
  • Mo‑NMR (⁹⁵/⁹⁷Mo): spectroscopy references summarizing relative sensitivity and usage. (chem.ch.huji.ac.il, ScienceDirect)
  • p‑nuclide context (⁹²,⁹⁴Mo): γ‑process/p‑process reviews. (Wikipedia, thomasrauscher.ch)

Next: Technetium — Tc (Z = 43).