Strontium-90

Properties and data of the isotope ⁹⁰Sr.

Content

Strontium-90 is a radioactive isotope that is produced as an artificial product primarily in nuclear fission and occurs in the fallout from nuclear explosions and nuclear accidents. In medicine, Sr-90 is used as a radioactive source for superficial radiation therapy for some types of cancer.

Sr-90 consists of a nucleus with 38 protons and 52 neutrons; this results in the mass number 90. The isotope is an alpha emitter with a half-life of about 29 years, which can be harmful to humans if ingested in large quantities. Strontium-90 can accumulate in bones and teeth and cause damage there.

General data

Name of the isotope:Strontium-90; Sr-90Symbol:⁹⁰Sr or 9038SrMass number A:90 (= number of nucleons)Atomic number Z:38 (= number of protons)Neutrons N:52Isotopic mass:89.9077279(16) u (atomic weight of Strontium-90)Nuclide mass:89.8868827 u (calculated nuclear mass without electrons)Mass excess:-85.95091 MeVMass defect:0.84019894799999 u (per nucleus)Nuclear binding energy:782.64027887 MeV (per nucleus)
8.6960031 MeV (average binding energy per nucleon)Separation energy:S_N = 7.8132(15) MeV (first neutron)
S_P = 11.528(6) MeV (first proton)Half-life:28.91(3) aDecay constant λ:7.602748918620 × 10^-10 s^-1Specific activity α:5144362349512.6 Bq g^-1
139.0368202571 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Charge radius:4.2611(37) femtometer fmYear of discovery:1948

Radioactive Decay

Strontium-90 decays in a β^--decay with the release of an electron to yttrium-90 (half-life 64 hours) and further to the stable zirconium-90 (emission of another electron and an antineutrino).

⁹⁰Sr has a specific activity of 5.21 TBq/g.

Half-life T_½ = 28.91(3) a respectively 9.11706 × 10⁸ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	⁹⁰Y	100%	0.5460(14) MeV

Parent Nuclides

Direct parent isotope is: ⁹⁰Rb.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 52) and isobaric (same nucleon number A = 90) with Strontium-90. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 52	Isobar A = 90
28	⁸⁰Ni
29	⁸¹Cu
30	⁸²Zn
31	⁸³Ga
32	⁸⁴Ge	⁹⁰Ge
33	⁸⁵As	⁹⁰As
34	⁸⁶Se	⁹⁰Se
35	⁸⁷Br	⁹⁰Br
36	⁸⁸Kr	⁹⁰Kr
37	⁸⁹Rb	⁹⁰Rb
38	⁹⁰Sr	⁹⁰Sr
39	⁹¹Y	⁹⁰Y
40	⁹²Zr	⁹⁰Zr
41	⁹³Nb	⁹⁰Nb
42	⁹⁴Mo	⁹⁰Mo
43	⁹⁵Tc	⁹⁰Tc
44	⁹⁶Ru	⁹⁰Ru
45	⁹⁷Rh	⁹⁰Rh
46	⁹⁸Pd	⁹⁰Pd
47	⁹⁹Ag
48	¹⁰⁰Cd
49	¹⁰¹In
50	¹⁰²Sn
51	¹⁰³Sb