Cesium-129
Properties and data of the isotope 129Cs.
See also: List of individual Cesium isotopes (and general data sources).
General data
Name of the isotope:Cesium-129; Cs-129Symbol:129Cs or 12955CsMass number A:129 (= number of nucleons)Atomic number Z:55 (= number of protons)Neutrons N:74Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):1.3454545454545 (= neutron-proton ratio)Neutron excess (N-Z):19Isotopic mass:128.906066(5) u (atomic weight of Cesium-129)Nuclide mass:128.8758961 u (calculated nuclear mass without electrons)Mass excess:-87.49896 MeVMass defect:1.165514544 u (per nucleus)Nuclear binding energy:1085.66980465 MeV (per nucleus)
8.416045 MeV (average binding energy per nucleon)Separation energy:SN = 9.639(7) MeV (first neutron)
SP = 4.928(5) MeV (first proton)Half-life:32.06(6) hDecay constant λ:5.841653018473 × 10-6 s-1Specific activity α:2.748379479071 × 10+16 Bq g-1
742805.26461403 Ci g-1Spin and parity:
(nuclear angular momentum)1/2+Magnetic dipole moment:μ(μN) = + 1.489(8)Nuclear g-factor:gl = 2.978Charge radius:4.7981(50) femtometer fmYear of discovery:1950
Radioactive Decay
Half-life T½ = 32.06(6) h (hours) respectively 1.18656 × 105 seconds s.
Decay
mode | Daughter | Probability | Decay energy | γ energy
(intensity) |
|---|
| EC/β+ | 129Xe | 100 % | 1.197(5) MeV | |
Parent Nuclides
Direct parent isotope is: 129Ba.
Isotones and Isobars
The following table shows the atomic nuclei that are isotonic (same neutron number N = 74) and isobaric (same nucleon number A = 129) with Cesium-129. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
| Z | Isotone N = 74 | Isobar A = 129 |
|---|
| 41 | 115Nb | |
| 42 | 116Mo | |
| 43 | 117Tc | |
| 44 | 118Ru | |
| 45 | 119Rh | |
| 46 | 120Pd | 129Pd |
| 47 | 121Ag | 129Ag |
| 48 | 122Cd | 129Cd |
| 49 | 123In | 129In |
| 50 | 124Sn | 129Sn |
| 51 | 125Sb | 129Sb |
| 52 | 126Te | 129Te |
| 53 | 127I | 129I |
| 54 | 128Xe | 129Xe |
| 55 | 129Cs | 129Cs |
| 56 | 130Ba | 129Ba |
| 57 | 131La | 129La |
| 58 | 132Ce | 129Ce |
| 59 | 133Pr | 129Pr |
| 60 | 134Nd | 129Nd |
| 61 | 135Pm | 129Pm |
| 62 | 136Sm | 129Sm |
| 63 | 137Eu | |
| 64 | 138Gd | |
| 65 | 139Tb | |
| 66 | 140Dy | |
| 67 | 141Ho | |
External data and identifiers
Last update: 2020-10-18
Perma link: https://www.chemlin.org/isotope/cesium-129
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