Magnesium-20

Properties and data of the isotope ²⁰Mg.

Contents

Magnesium-20 is a radioisotope of the chemical element magnesium, which has 8 neutrons in its atomic nucleus in addition to the element-specific 12 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 20. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ²⁰Mg is exclusively for academic purposes.

The proton-rich isotope was first observed during irradiation of enriched magnesium-24 with alpha particles accelerated to 156 MeV [1]:

²⁴Mg(α,⁸He)²⁰Mg.

General data

Name of the isotope:Magnesium-20; Mg-20Symbol:²⁰Mg or 2012MgMass number A:20 (= number of nucleons)Atomic number Z:12 (= number of protons)Neutrons N:8Isotopic mass:20.0187631(20) u (atomic weight of Magnesium-20)Nuclide mass:20.0121802 u (calculated nuclear mass without electrons)Mass excess:17.47772 MeVMass defect:0.144456612 u (per nucleus)Nuclear binding energy:134.56046734 MeV (per nucleus)
6.72802337 MeV (average binding energy per nucleon)Separation energy:S_N = 22.432(60) MeV (first neutron)
S_P = 2.741(11) MeV (first proton)Half-life:90.4(7) msDecay constant λ:7.667557307079 s^-1Specific activity α:2.308755507743 × 10⁺²³ Bq g^-1
6239879750657.8 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Mirror nucleus:Oxygen-20Year of discovery:1974

Radioactive Decay

Half-life T_½ = 90.4(7) ms respectively 9.04 × 10^-2 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β⁺	²⁰Na	69.7 %	10.6272(22) MeV
β⁺, p	¹⁹Ne	30.3(12) %	8.530 MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 8) and isobaric (same nucleon number A = 20) with Magnesium-20. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 8	Isobar A = 20
2	¹⁰He
3	¹¹Li
4	¹²Be
5	¹³B	²⁰B
6	¹⁴C	²⁰C
7	¹⁵N	²⁰N
8	¹⁶O	²⁰O
9	¹⁷F	²⁰F
10	¹⁸Ne	²⁰Ne
11	¹⁹Na	²⁰Na
12	²⁰Mg	²⁰Mg
13	²¹Al
14	²²Si

Data changes (history)

In 2016, a more accurate value for the half-life of magnesium-20 was published: T_1/2 = 91.4(10) ms [2].

External data and identifiers

Adopted Levels, Gammas:NuDat 20Mg

Literature and References

[1] - R. G. H. Robertson, S. Martin, W. R. Falk, D. Ingham, A. Djaloeis:
Highly Proton-Rich T_z = -2 Nuclides: ⁸C and ²⁰Mg.
In: Physical Review Letters, 32, 1207, (1974), DOI 10.1103/PhysRevLett.32.1207.

[2] - IDS Collaboration, M. V. Lund et al.:
Beta-delayed proton emission from ²⁰Mg.
In: The European Physical Journal A, 52, 304, (2016), DOI 10.1140/epja/i2016-16304-x.