Argon-51

Properties and data of the isotope ⁵¹Ar.

Content

General data

Name of the isotope:Argon-51; Ar-51Symbol:⁵¹Ar or 5118ArMass number A:51 (= number of nucleons)Atomic number Z:18 (= number of protons)Neutrons N:33Isotopic mass:50.99280(64) u (atomic weight of Argon-51)Nuclide mass:50.9829257 u (calculated nuclear mass without electrons)Mass excess:-6.70676 MeVMass defect:0.433992804 u (per nucleus)Nuclear binding energy:404.26169297 MeV (per nucleus)
7.92669986 MeV (average binding energy per nucleon)Separation energy:S_N = 1.43(78) MeV (first neutron)
S_P = 21.72(85) MeV (first proton)Half-life:> 60 msDecay constant λ:11.552453009332 s^-1Specific activity α:1.39140998 × 10⁺²³ Bq g^-1
3760567529729.7 Ci g^-1Spin and parity:
(nuclear angular momentum)3/2-Year of discovery:1989

Radioactive Decay

Half-life T_½ = > 60 ms respectively 6 × 10^-2 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	⁵¹K	100 %	15.83(60) MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 33) and isobaric (same nucleon number A = 51) with Argon-51. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 33	Isobar A = 51
16	⁴⁹S
17	⁵⁰Cl	⁵¹Cl
18	⁵¹Ar	⁵¹Ar
19	⁵²K	⁵¹K
20	⁵³Ca	⁵¹Ca
21	⁵⁴Sc	⁵¹Sc
22	⁵⁵Ti	⁵¹Ti
23	⁵⁶V	⁵¹V
24	⁵⁷Cr	⁵¹Cr
25	⁵⁸Mn	⁵¹Mn
26	⁵⁹Fe	⁵¹Fe
27	⁶⁰Co	⁵¹Co
28	⁶¹Ni	⁵¹Ni
29	⁶²Cu
30	⁶³Zn
31	⁶⁴Ga
32	⁶⁵Ge
33	⁶⁶As
34	⁶⁷Se
35	⁶⁸Br
36	⁶⁹Kr