Chlorine-31

Properties and data of the isotope ³¹Cl.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Chlorine-31 is a radioisotope of the chemical element chlorine, which has 14 neutrons in its atomic nucleus in addition to the element-specific 17 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 31. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ³¹Cl is exclusively for academic purposes and experimental research.

The isotope was first described in 1977 [1]; according to this, chlorine-31 was formed by the irradiation of argon-36 gas with 70 MeV helium-3 ions through the nuclear reaction

³⁶Ar(³He,⁸Li)³¹Cl.

See also: List of individual Chlorine isotopes (and general data sources).

General data

Name of the isotope:Chlorine-31; Cl-31Symbol:³¹Cl or 3117ClMass number A:31 (= number of nucleons)Atomic number Z:17 (= number of protons)Neutrons N:14Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):0.82352941176471 (= neutron-proton ratio)Neutron excess (N-Z):-3Isotopic mass:30.992448(4) u (atomic weight of Chlorine-31)Nuclide mass:30.9831223 u (calculated nuclear mass without electrons)Mass excess:-7.03464 MeVMass defect:0.261886368 u (per nucleus)Nuclear binding energy:243.94558047 MeV (per nucleus)
7.86921227 MeV (average binding energy per nucleon)Separation energy:S_N = 19.780(24) MeV (first neutron)
S_P = 0.264(3) MeV (first proton)Half-life:190(1) msDecay constant λ:3.6481430555787 s^-1Specific activity α:7.088704639695 × 10⁺²² Bq g^-1
1915866118836.5 Ci g^-1Spin and parity:
(nuclear angular momentum)3/2+Mirror nucleus:Silicon-31Year of discovery:1977

Radioactive Decay

Half-life T_½ = 190(1) ms respectively 1.90 × 10^-1 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β⁺	³¹S	97.6 %	12.008(3) MeV
β⁺, p	³⁰P	2.4(2) %	5.844 MeV

Parent Nuclides

Direct parent isotope is: ³¹Ar.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 14) and isobaric (same nucleon number A = 31) with Chlorine-31. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 14	Isobar A = 31
5	¹⁹B
6	²⁰C
7	²¹N
8	²²O
9	²³F	³¹F
10	²⁴Ne	³¹Ne
11	²⁵Na	³¹Na
12	²⁶Mg	³¹Mg
13	²⁷Al	³¹Al
14	²⁸Si	³¹Si
15	²⁹P	³¹P
16	³⁰S	³¹S
17	³¹Cl	³¹Cl
18	³²Ar	³¹Ar
19	³³K	³¹K
20	³⁴Ca

External data and identifiers

Adopted Levels, Gammas:NuDat 31Cl

Literature and References

[1] - W. Benenson, D. Mueller, E. Kashy, H. Nann, L. W. Robinson:
Mass of ²⁷P and ³¹Cl.
In: Physical Review C, 15, 1187, (1977), DOI 10.1103/PhysRevC.15.1187.