Notable Isotopes 
124Xe [70 neutrons]
Abundance: 0.1%
Half life: 1.1 x 1017 years [ Double Electron Capture ]
Decay Energy: ? MeVDecays to 124Te.
125Xe [71 neutrons]Abundance: synthetic
Half life: 16.9 hours [ Electron Capture ]
Decay Energy: 1.652 MeVDecays to 125I.
126Xe [72 neutrons]Abundance: 0.09%
Stable with 72 neutrons
127Xe [73 neutrons]Abundance: synthetic
Half life: 36.4 days [ Electron Capture ]
Decay Energy: 0.662 MeVDecays to 127I.
128Xe [74 neutrons]Abundance: 1.91%
Stable with 74 neutrons
129Xe [75 neutrons]Abundance: 26.4%
Stable with 75 neutrons
| Excess 129Xe found in carbon dioxide well gases from New Mexico was believed to be from the decay of mantle-derived gases soon after Earth's formation. |
130Xe [76 neutrons]Abundance: 4.1%
Stable with 76 neutrons
131Xe [77 neutrons]Abundance: 21.29%
Stable with 77 neutrons
132Xe [78 neutrons]Abundance: 26.9%
Stable with 78 neutrons
133Xe [79 neutrons]Abundance: synthetic
Half life: 5.243 days [ beta- ]
Decay Energy: 0.427 MeVDecays to 133Cs.
134Xe [80 neutrons]Abundance: 10.4%
Stable with 80 neutrons
135Xe [81 neutrons]Abundance: synthetic
Half life: 9.10 hours [ beta- ]
Decay Energy: 1.16 MeVDecays to 135Cs.
| 135Xe is of considerable significance in the operation of nuclear fission reactors. 135Xe has a huge cross section for thermal neutrons, 2.6 x 106 barns, so it acts as a neutron absorber or "poison" that can slow or stop the chain reaction after a period of operation. |
136Xe [82 neutrons]Abundance: 8.9%
Half life: 2.36 x 1021 years [ beta- ]
Decay Energy: ? MeVDecays to 136Ba.