Mercury-199
Properties and data of the isotope 199Hg.
Mercury-199 is a stable isotope of the chemical element mercury, which has 119 neutrons in its atomic nucleus in addition to the element-specific 80 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 199.
The identification of Hg-201 as a distinct isotope was reported in 1925; the evidence was obtained using mass spectra [1].
See also: List of individual Mercury isotopes (and general data sources).
General data
Name of the isotope:Mercury-199; Hg-199Symbol:199Hg or 19980HgMass number A:199 (= number of nucleons)Atomic number Z:80 (= number of protons)Neutrons N:119Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.4875 (= neutron-proton ratio)Neutron excess (N-Z):39Isotopic mass:198.968281(3) u (atomic weight of Mercury-199)Nuclide mass:198.9243994 u (calculated nuclear mass without electrons)Mass excess:-29.54606 MeVMass defect:1.688846564 u (per nucleus)Nuclear binding energy:1573.15044129 MeV (per nucleus)
7.9052786 MeV (average binding energy per nucleon)Separation energy:SN = 6.6631(6) MeV (first neutron)
SP = 7.2542(6) MeV (first proton)Half-life:stableSpin and parity:
(nuclear angular momentum)1/2-Magnetic dipole moment:μ(μN) = + 0.5058855(9)Charge radius:5.4474(31) femtometer fmYear of discovery:1925
Radioactive Decay
Half-life T½ = stable.
Decay
mode | Daughter | Probability | Decay energy | γ energy
(intensity) |
|---|
| α ? | | | | |
Parent Nuclides
Direct parent isotopes are: 199Tl, 199Au.
Occurrence
Comparison of the natural Mercury isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):
| | Atomic Mass ma | Quantity | Half-life | Spin |
|---|
Mercury
Isotopic mixture | 200.592 u | 100 % | | |
| Isotope 196Hg | 195.96583(2) u | 0.15(1) % | stable | 0+ |
| Isotope 198Hg | 197.966769(3) u | 10.04(3) % | stable | 0+ |
| Isotope 200Hg | 199.968327(3) u | 23.14(9) % | stable | 0+ |
| Isotope 202Hg | 201.970643(5) u | 29.74(13) % | stable | 0+ |
| Isotope 204Hg | 203.973494(3) u | 6.82(4) % | stable | 0+ |
| Isotope 201Hg | 200.970303(5) u | 13.17(9) % | stable | 3/2- |
| Isotope 199Hg | 198.968281(3) u | 16.94(12) % | stable | 1/2- |
NMR data
Nuclear magnetic properties and parameters of the NMR active Nuclide 199Hg
Isotope:199Hg-NMRQuantity:16.94(12) %Spin:1/2-Nuclearmagnetic moment
μ/μN:+ 0.5058855(9)Gyromagnetic ratio γ:4.8457916 · 107 rad T-1 s-1
7.71232 MHz T-1Nuclear g-factor:gl = 1.011771Resonance frequency:v0 = 7.7123 MHz at 1 TRelative Sensitivity:[related to 1H = 1.000]:
0.00594 (H0 = const.)
0.1811 (v0 = const.)
0.001 (at natural abundance)
relative receptivity as compared to 13C:
5.89 (at natural abundance)Reference compound:
(conditions)The IUPAC (2001) lists pure Dimethylmercury (CH3)2Hg as a reference substance for 199Hg NMR spectroscopy and (justifiably) advises against its direct use due to its high toxicity. As an alternative, the less toxic compounds mercury(II) chloride and mercury diperchlorate Hg(ClO4)2 (0.1 M in deuterium oxide D2O) were used; its chemical shift of the perchlorate is -2250 ppm relative to dimethylmercury.Frequency ratio:Ξ(199Hg) = 17.910822 % [based on the reference substance]
Nuclear Isomers
Nuclear isomers or excited states with the activation energy in keV related to the ground state.
| Nuclear Isomer | Excitation Energy | Half-life | Spin |
|---|
| 199mHg | 532.48(10) keV | 42.67(9) min | 13/2+ |
Isotones and Isobars
The following table shows the atomic nuclei that are isotonic (same neutron number N = 119) and isobaric (same nucleon number A = 199) with Mercury-199. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
| Z | Isotone N = 119 | Isobar A = 199 |
|---|
| 73 | 192Ta | |
| 74 | 193W | |
| 75 | 194Re | 199Re |
| 76 | 195Os | 199Os |
| 77 | 196Ir | 199Ir |
| 78 | 197Pt | 199Pt |
| 79 | 198Au | 199Au |
| 80 | 199Hg | 199Hg |
| 81 | 200Tl | 199Tl |
| 82 | 201Pb | 199Pb |
| 83 | 202Bi | 199Bi |
| 84 | 203Po | 199Po |
| 85 | 204At | 199At |
| 86 | 205Rn | 199Rn |
| 87 | 206Fr | 199Fr |
| 88 | 207Ra | |
| 89 | 208Ac | |
| 90 | 209Th | |
| 91 | 210Pa | |
External data and identifiers
Literature and References
[1] - F. W. Aston:
The Isotopes of Mercury.
In: Nature, 116, 208, (1925), DOI 10.1038/116208b0.
[2] - David Z. Zee, Christopher P. Singer, Thomas V. O´Halloran:
Chemical-Shift Standards for 199Hg NMR Spectroscopy, 25 Years Later.
In: Inorganic Chemistry, 61 ,35, (2022), DOI 10.1021/acs.inorgchem.2c02183.
Last update: 2025-12-18
Perma link: https://www.chemlin.org/isotope/mercury-199
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