Zirconium-91
Properties and data of the isotope 91Zr.
Zirconium-91 is a stable isotope of the chemical element zirconium, which has 51 neutrons in its atomic nucleus in addition to the element-specific 40 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 91. Natural terrestrial Zr deposits consist of 11.22% Zr-91.
The first identification of Zirconium-91 was achieved using an anode discharge tube coupled to a Cavendish mass spectrograph [1].
See also: List of individual Zirconium isotopes (and general data sources).
General data
Name of the isotope:Zirconium-91; Zr-91Symbol:91Zr or 9140ZrMass number A:91 (= number of nucleons)Atomic number Z:40 (= number of protons)Neutrons N:51Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.275 (= neutron-proton ratio)Neutron excess (N-Z):11Isotopic mass:90.90564021(10) u (atomic weight of Zirconium-91)Nuclide mass:90.883698 u (calculated nuclear mass without electrons)Mass excess:-87.89558 MeVMass defect:0.849271786 u (per nucleus)Nuclear binding energy:791.09157303 MeV (per nucleus)
8.69331399 MeV (average binding energy per nucleon)Separation energy:SN = 8.19436(15) MeV (first neutron)
SP = 8.6877(4) MeV (first proton)Half-life:stableSpin and parity:
(nuclear angular momentum)5/2+Magnetic dipole moment:μ(μN) = -1.3022(4)Charge radius:4.2845(13) femtometer fmYear of discovery:1934
Parent Nuclides
Direct parent isotopes are: 91Nb, 91Y.
Occurrence
Comparison of the natural Zirconium isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):
| | Atomic Mass ma | Quantity | Half-life | Spin |
|---|
Zirconium
Isotopic mixture | 91.222 u | 100 % | | |
| Isotope 90Zr | 89.90470(2) u | 51.45(4) % | stable | 0+ |
| Isotope 92Zr | 91.90503(2) u | 17.15(3) % | stable | 0+ |
| Isotope 94Zr | 93.90631(2) u | 17.38(4) % | stable | 0+ |
| Isotope 96Zr | 95.90827(2) u | 2.80(2) % | 2.0(4) × 1019 a | 0+ |
| Isotope 91Zr | 90.90564021(10) u | 11.22(5) % | stable | 5/2+ |
NMR data
Nuclear magnetic properties and parameters of the NMR active Nuclide 91Zr
Isotope:91Zr-NMRQuantity:11.22(5) %Spin:5/2+Nuclearmagnetic moment
μ/μN:-1.3022(4)Gyromagnetic ratio γ:-2.49743 · 107 rad T-1 s-1
-3.97478 MHz T-1Nuclear g-factor:gl = -0.52088Quadrupole moment Q:-0.176(3) barn (100 fm2)Line width parameter (factor):l = 99.12 fm4Resonance frequency:v0 = 3.9748 MHz at 1 TRelative Sensitivity:[related to 1H = 1.000]:
0.00949 (H0 = const.)
1.0892 (v0 = const.)
0.00107 (at natural abundance)
relative receptivity as compared to 13C:
6.26 (at natural abundance)Reference compound:
(conditions)Saturated solution of zirconocene dichloride in dichloromethane, containing a small amount (≤ 10 %) of benzene-d6.Frequency ratio:Ξ(91Zr) = 9.296298 % [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 |
|---|
| 91mZr | 3167.3(4) keV | 4.35(14) μs | (21/2+) |
Isotones and Isobars
The following table shows the atomic nuclei that are isotonic (same neutron number N = 51) and isobaric (same nucleon number A = 91) with Zirconium-91. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
| Z | Isotone N = 51 | Isobar A = 91 |
|---|
| 28 | 79Ni | |
| 29 | 80Cu | |
| 30 | 81Zn | |
| 31 | 82Ga | |
| 32 | 83Ge | |
| 33 | 84As | 91As |
| 34 | 85Se | 91Se |
| 35 | 86Br | 91Br |
| 36 | 87Kr | 91Kr |
| 37 | 88Rb | 91Rb |
| 38 | 89Sr | 91Sr |
| 39 | 90Y | 91Y |
| 40 | 91Zr | 91Zr |
| 41 | 92Nb | 91Nb |
| 42 | 93Mo | 91Mo |
| 43 | 94Tc | 91Tc |
| 44 | 95Ru | 91Ru |
| 45 | 96Rh | 91Rh |
| 46 | 97Pd | 91Pd |
| 47 | 98Ag | |
| 48 | 99Cd | |
| 49 | 100In | |
| 50 | 101Sn | |
External data and identifiers
Literature and References
[1] - F. W. Aston:
Constitution of Hafnium and other Elements.
In: Nature, 133, 684, (1934), DOI 10.1038/133684b0.
Last update: 2026-01-26
Perma link: https://www.chemlin.org/isotope/zirconium-91
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