Selenium-81
Properties and data of the isotope 81Se.
See also: List of individual Selenium isotopes (and general data sources).
General data
Name of the isotope:Selenium-81; Se-81Symbol:81Se or 8134SeMass number A:81 (= number of nucleons)Atomic number Z:34 (= number of protons)Neutrons N:47Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.3823529411765 (= neutron-proton ratio)Neutron excess (N-Z):13Isotopic mass:80.9179930(11) u (atomic weight of Selenium-81)Nuclide mass:80.8993419 u (calculated nuclear mass without electrons)Mass excess:-76.38903 MeVMass defect:0.75530914000001 u (per nucleus)Nuclear binding energy:703.56593206 MeV (per nucleus)
8.68599916 MeV (average binding energy per nucleon)Separation energy:SN = 6.7008(3) MeV (first neutron)
SP = 11.463(3) MeV (first proton)Half-life:18.45(12) minDecay constant λ:0.00062614921459796 s-1Specific activity α:4.713448462059 × 10+18 Bq g-1
127390498.97458 Ci g-1Spin and parity:
(nuclear angular momentum)1/2-Year of discovery:1949
Radioactive Decay
Half-life T½ = 18.45(12) min (minutes) respectively 1.107 × 103 seconds s.
Decay
mode | Daughter | Probability | Decay energy | γ energy
(intensity) |
|---|
| β- | 81Br | 100 % | 1.5880(14) MeV | |
Parent Nuclides
Direct parent isotope is: 81As.
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 |
|---|
| 81mSe | 103.00(6) keV | 57.28(2) min | 7/2+ |
Isotones and Isobars
The following table shows the atomic nuclei that are isotonic (same neutron number N = 47) and isobaric (same nucleon number A = 81) with Selenium-81. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
| Z | Isotone N = 47 | Isobar A = 81 |
|---|
| 26 | 73Fe | |
| 27 | 74Co | |
| 28 | 75Ni | |
| 29 | 76Cu | 81Cu |
| 30 | 77Zn | 81Zn |
| 31 | 78Ga | 81Ga |
| 32 | 79Ge | 81Ge |
| 33 | 80As | 81As |
| 34 | 81Se | 81Se |
| 35 | 82Br | 81Br |
| 36 | 83Kr | 81Kr |
| 37 | 84Rb | 81Rb |
| 38 | 85Sr | 81Sr |
| 39 | 86Y | 81Y |
| 40 | 87Zr | 81Zr |
| 41 | 88Nb | 81Nb |
| 42 | 89Mo | 81Mo |
| 43 | 90Tc | |
| 44 | 91Ru | |
| 45 | 92Rh | |
| 46 | 93Pd | |
| 47 | 94Ag | |
| 48 | 95Cd | |
| 49 | 96In | |
External data and identifiers
Last update: 2020-10-14
Perma link: https://www.chemlin.org/isotope/selenium-81
© 1996 - 2026 ChemLin
