Argon-31

Properties and data of the isotope ³¹Ar.

Content

General data

Name of the isotope:Argon-31; Ar-31Symbol:³¹Ar or 3118ArMass number A:31 (= number of nucleons)Atomic number Z:18 (= number of protons)Neutrons N:13Isotopic mass:31.01216(22) u (atomic weight of Argon-31)Nuclide mass:31.0022857 u (calculated nuclear mass without electrons)Mass excess:11.32697 MeVMass defect:0.241334484 u (per nucleus)Nuclear binding energy:224.80162384 MeV (per nucleus)
7.25166529 MeV (average binding energy per nucleon)Separation energy:S_N = 17.68(29) MeV (first neutron)
S_P = 0.41(28) MeV (first proton)Half-life:14.4(6) msDecay constant λ:48.135220872218 s^-1Specific activity α:9.35087356182 × 10⁺²³ Bq g^-1
25272631248184 Ci g^-1Spin and parity:
(nuclear angular momentum)5/2+Mirror nucleus:Aluminium-31Year of discovery:1986

Radioactive Decay

Half-life T_½ = 14.4(6) ms respectively 1.44 × 10^-2 seconds s.

Decay mode	Daughter	Probability	Decay energy
EE/β⁺	³¹Cl		18.36(20) MeV
β⁺, p	³⁰S	63(7) %
β⁺, 2p	²⁹P	7.2(11) %
β⁺, 3p	²⁸Si	2.1(10) %

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 13) and isobaric (same nucleon number A = 31) with Argon-31. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 13	Isobar A = 31
5	¹⁸B
6	¹⁹C
7	²⁰N
8	²¹O
9	²²F	³¹F
10	²³Ne	³¹Ne
11	²⁴Na	³¹Na
12	²⁵Mg	³¹Mg
13	²⁶Al	³¹Al
14	²⁷Si	³¹Si
15	²⁸P	³¹P
16	²⁹S	³¹S
17	³⁰Cl	³¹Cl
18	³¹Ar	³¹Ar
19	³²K