Magnesium-25

Properties and data of the isotope ²⁵Mg.

Contents

General Data

Parent Nuclides

NMR Data

Isotones und Isobares

Literature

Magnesium-25 is a stable isotope of the chemical element magnesium, which has 13 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 25. ²⁵Mg is one of the three isotopes that make up the earth's natural magnesium deposits (see below).

In 1920, the physicist Arthur Jeffrey Dempster described the isotopic composition of magnesium for the first time. For his experiments, he used an apparatus for positive ray analysis; the cylindrical anode contained the magnesium and was irradiated with electrons [1].

General data

Name of the isotope:Magnesium-25; Mg-25Symbol:²⁵Mg or 2512MgMass number A:25 (= number of nucleons)Atomic number Z:12 (= number of protons)Neutrons N:13Isotopic mass:24.9858370(3) u (atomic weight of Magnesium-25)Nuclide mass:24.9792541 u (calculated nuclear mass without electrons)Mass excess:-13.19275 MeVMass defect:0.220707292 u (per nucleus)Nuclear binding energy:205.58751825 MeV (per nucleus)
8.22350073 MeV (average binding energy per nucleon)Separation energy:S_N = 7.33053(5) MeV (first neutron)
S_P = 12.06385(5) MeV (first proton)Half-life:stableSpin and parity:
(nuclear angular momentum)5/2+Magnetic dipole moment:μ(μ_N) = -0.85533(3)Charge radius:3.0284(22) femtometer fmMirror nucleus:Aluminium-25Year of discovery:1920

Parent Nuclides

Direct parent isotopes are: ²⁵Al, ²⁵Na.

Occurrence

Comparison of the natural Magnesium isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):

	Atomic Mass m_a	Quantity	Half-life	Spin
Magnesium Isotopic mixture	24.305 u	100 %
Isotope ²⁴Mg	23.98504170(9) u	78.965(49) % [78.88 - 79.05 %]	stable	0+
Isotope ²⁵Mg	24.9858370(3) u	10.011 % [9.988 - 10.034 %]	stable	5/2+
Isotope ²⁶Mg	25.9825930(2) u	11.024 % [10.96 - 11.09 %]	stable	0+

NMR data

Nuclear magnetic properties of the NMR active Nuclide ²⁵Mg

Isotope:²⁵Mg-NMRQuantity:10.011 % [9.988 - 10.034 %]Spin:5/2+Nuclearmagnetic moment
μ/μ_N:-0.85533(3)Gyromagnetic ratio γ:- 1.639 · 10⁷ rad T^-1 s^-1Nuclear g-factor:g_l = -0.342132Quadrupole moment Q:+ 0.1994(20) barn (100 fm²)Resonance frequency:v₀ = 2.6083 at 1 TFrequency ratio:Ξ(²⁵Mg) = 6.121635 %Relative Sensitivity:0.002698 (H₀ = const.)
0.7147 (v₀ = const.)
[related to ¹H = 1.000]Reference compound:
(conditions)Solution of magnesium chloride MgCl₂ (11 M) in deuterium oxide D₂O.

Magnesium-25 has the only NMR-active atomic nucleus of the three natural magnesium isotopes. The nuclide is quadrupolar with a spin of 5/2 and has only a low sensitivity. The NMR signal width is narrow in symmetrical environments and increases with the asymmetry of the environment, such as in Grignard compounds. The chemical shift of inorganic magnesium is strongly solvent-dependent. Overall, ²⁵NMR spectroscopy is a rarely used special application.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 13) and isobaric (same nucleon number A = 25) with Magnesium-25. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

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

External data and identifiers

Adopted Levels, Gammas:NuDat 25Mg

Literature and References

[1] - A. J. Dempster:
Positive Ray Analysis of Lithium and Magnesium.
In: Physical Review, 18, 415, (1921), DOI 10.1103/PhysRev.18.415.

[2] - Jair C.C. Freitas, Mark E. Smith:
Recent Advances in Solid-State ²⁵Mg NMR Spectroscopy.
In: Annual Reports on NMR Spectroscopy, 75, (2012), DOI 10.1016/B978-0-12-397018-3.00002-8.