Magnesium-28

Properties and data of the isotope ²⁸Mg.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Magnesium-28 is a radioisotope of the chemical element magnesium, which has 16 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 28. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ²⁸Mg is exclusively for academic purposes.

According to a report from 1934, the neutron-rich isotope was first observed and identified during irradiation of silicon-30 with γ-rays (100 MeV) and magnesium-26 with α-particles (39 MeV) [1]:

³⁰Si(γ,2p)²⁸Mg,

²⁶Mg(α,2p)²⁸Mg.

General data

Name of the isotope:Magnesium-28; Mg-28Symbol:²⁸Mg or 2812MgMass number A:28 (= number of nucleons)Atomic number Z:12 (= number of protons)Neutrons N:16Isotopic mass:27.98387543(28) u (atomic weight of Magnesium-28)Nuclide mass:27.9772925 u (calculated nuclear mass without electrons)Mass excess:-15.01994 MeVMass defect:0.24866361 u (per nucleus)Nuclear binding energy:231.62866073 MeV (per nucleus)
8.27245217 MeV (average binding energy per nucleon)Separation energy:S_N = 8.50467(27) MeV (first neutron)
S_P = 16.791(4) MeV (first proton)Half-life:20.915(9) hDecay constant λ:9.20587537599 × 10^-6 s^-1Specific activity α:2.053299194564 × 10⁺¹⁷ Bq g^-1
5549457.2826073 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Charge radius:0 femtometer fmMirror nucleus:Sulfur-28Year of discovery:1953

Radioactive Decay

Half-life T_½ = 20.915(9) h (hours) respectively 7.5294 × 10⁴ seconds s.

Decay mode	Daughter	Probability	Decay energy	Details	γ energy (intensity)
β^-	²⁸Al	100 %	1.83077(27) MeV	β^-: 0.0652(7) MeV [4.9(10) %] β^-: 0.1560(8) MeV [94.8(10) %] β^-: 0.3192(9) MeV [0.31(4) %]	0.0306383(7) MeV [89 %] 0.4006(2) MeV [35.9 %] 0.9417(4) MeV [36.3 %] 1.3422(2) MeV [54.0 %] 1.3728(2) MeV [4.7 %] 1.5894(4) MeV [4.7 %]

Parent Nuclides

Direct parent isotopes are: ²⁸Na, ²⁹Na.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 16) and isobaric (same nucleon number A = 28) with Magnesium-28. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 16	Isobar A = 28
5	²¹B
6	²²C
7	²³N
8	²⁴O	²⁸O
9	²⁵F	²⁸F
10	²⁶Ne	²⁸Ne
11	²⁷Na	²⁸Na
12	²⁸Mg	²⁸Mg
13	²⁹Al	²⁸Al
14	³⁰Si	²⁸Si
15	³¹P	²⁸P
16	³²S	²⁸S
17	³³Cl	²⁸Cl
18	³⁴Ar
19	³⁵K
20	³⁶Ca
21	³⁷Sc
22	³⁸Ti