Cesium-126
Properties and data of the isotope 126Cs.
See also: list of Cesium isotopes.
General data
Name of the isotope:Cesium-126; Cs-126Symbol:126Cs or 12655CsMass number A:126 (= number of nucleons)Atomic number Z:55 (= number of protons)Neutrons N:71Isotopic mass:125.909446(11) u (atomic weight of Cesium-126)Nuclide mass:125.8792761 u (calculated nuclear mass without electrons)Mass excess:-84.35051 MeVMass defect:1.136139796 u (per nucleus)Nuclear binding energy:1058.30740314 MeV (per nucleus)
8.3992651 MeV (average binding energy per nucleon)Separation energy:SN = 8.334(13) MeV (first neutron)
SP = 4.446(11) MeV (first proton)Half-life:1.64(2) minDecay constant λ:0.0070441786642271 s-1Specific activity α:3.393682892682 × 10+19 Bq g-1
917211592.617 Ci g-1Spin and parity:
(nuclear angular momentum)1+Magnetic dipole moment:μ(μN) = + 0.776(4)Quadrupole moment Q:- 0.68(2) barn (100 fm2)Nuclear g-factor:gl = 0.776Charge radius:4.7872(56) femtometer fmYear of discovery:1954
Radioactive Decay
Half-life T½ = 1.64(2) min (minutes) respectively 9.84 × 101 seconds s.
Decay
mode | Daughter | Probability | Decay energy | γ energy
(intensity) |
|---|
| EC/β+ | 126Xe | 100 % | 4.796(11) MeV | |
Parent Nuclides
Direct parent isotope is: 126Ba.
Nuclear Isomers
Nuclear isomers or excited states with the activation energy in keV related to the ground state.
| Nuclear Isomer | Excitation Energy | Half-life | Spin |
|---|
| 126m1Cs | 273.0(7) keV | 1 μs | |
| 126m2Cs | 596.1(11) keV | 171(14) μs | |
Isotones and Isobars
The following table shows the atomic nuclei that are isotonic (same neutron number N = 71) and isobaric (same nucleon number A = 126) with Cesium-126. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
| Z | Isotone N = 71 | Isobar A = 126 |
|---|
| 40 | 111Zr | |
| 41 | 112Nb | |
| 42 | 113Mo | |
| 43 | 114Tc | |
| 44 | 115Ru | |
| 45 | 116Rh | 126Rh |
| 46 | 117Pd | 126Pd |
| 47 | 118Ag | 126Ag |
| 48 | 119Cd | 126Cd |
| 49 | 120In | 126In |
| 50 | 121Sn | 126Sn |
| 51 | 122Sb | 126Sb |
| 52 | 123Te | 126Te |
| 53 | 124I | 126I |
| 54 | 125Xe | 126Xe |
| 55 | 126Cs | 126Cs |
| 56 | 127Ba | 126Ba |
| 57 | 128La | 126La |
| 58 | 129Ce | 126Ce |
| 59 | 130Pr | 126Pr |
| 60 | 131Nd | 126Nd |
| 61 | 132Pm | 126Pm |
| 62 | 133Sm | |
| 63 | 134Eu | |
| 64 | 135Gd | |
| 65 | 136Tb | |
External data and identifiers
Last update: 2020-10-18
Perma link: https://www.chemlin.org/isotope/cesium-126
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