Selenium-90

Properties and data of the isotope ⁹⁰Se.

Content

General data

Name of the isotope:Selenium-90; Se-90Symbol:⁹⁰Se or 9034SeMass number A:90 (= number of nucleons)Atomic number Z:34 (= number of protons)Neutrons N:56Isotopic mass:89.94010(35) u (atomic weight of Selenium-90)Nuclide mass:89.9214489 u (calculated nuclear mass without electrons)Mass excess:-55.79649 MeVMass defect:0.811186384 u (per nucleus)Nuclear binding energy:755.61524958 MeV (per nucleus)
8.395725 MeV (average binding energy per nucleon)Separation energy:S_N = 4.88(33) MeV (first neutron)
S_P = 16.29(44) MeV (first proton)Half-life:195 msDecay constant λ:3.5546009259484 s^-1Specific activity α:2.405203087294 × 10⁺²² Bq g^-1
650054888458.03 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Year of discovery:1994

Radioactive Decay

Half-life T_½ = 195 ms respectively 1.95 × 10^-1 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	⁹⁰Br		8.20(33) MeV
β^-, n	⁸⁹Br	?	4.40(33) MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 56) and isobaric (same nucleon number A = 90) with Selenium-90. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 56	Isobar A = 90
31	⁸⁷Ga
32	⁸⁸Ge	⁹⁰Ge
33	⁸⁹As	⁹⁰As
34	⁹⁰Se	⁹⁰Se
35	⁹¹Br	⁹⁰Br
36	⁹²Kr	⁹⁰Kr
37	⁹³Rb	⁹⁰Rb
38	⁹⁴Sr	⁹⁰Sr
39	⁹⁵Y	⁹⁰Y
40	⁹⁶Zr	⁹⁰Zr
41	⁹⁷Nb	⁹⁰Nb
42	⁹⁸Mo	⁹⁰Mo
43	⁹⁹Tc	⁹⁰Tc
44	¹⁰⁰Ru	⁹⁰Ru
45	¹⁰¹Rh	⁹⁰Rh
46	¹⁰²Pd	⁹⁰Pd
47	¹⁰³Ag
48	¹⁰⁴Cd
49	¹⁰⁵In
50	¹⁰⁶Sn
51	¹⁰⁷Sb
52	¹⁰⁸Te
53	¹⁰⁹I
54	¹¹⁰Xe