Francium-217

Properties and data of the isotope ²¹⁷Fr.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Francium-217 is a radioisotope of the chemical element francium, which has 130 neutrons in its atomic nucleus in addition to the element-specific 87 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 217. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ²¹⁷Fr is exclusively for academic purposes abd experimental research.

In 1968, a report was published describing, among other things, the short-lived isotope francium-217. In the experiments described therein, protons with energies of 32 to 41.6 MeV collided with enriched uranium-233, initially producing the previously unknown neptunium-229 in the reaction ²³³U(p,5n)²²⁹Np. Upon examination of the decay chains, the isotope francium-217 was identified in the branch of the daughter nuclide protactinium-225 [1]. However, the authors noted that the observation of this nuclide had already been described in an unpublished dissertation.

See also: List of individual Francium isotopes (and general data sources).

General data

Name of the isotope:Francium-217; Fr-217Symbol:²¹⁷Fr or 21787FrMass number A:217 (= number of nucleons)Atomic number Z:87 (= number of protons)Neutrons N:130Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):1.4942528735632 (= neutron-proton ratio)Neutron excess (N-Z):43Isotopic mass:217.004632(7) u (atomic weight of Francium-217)Nuclide mass:216.9569114 u (calculated nuclear mass without electrons)Mass excess:4.31468 MeVMass defect:1.802584864 u (per nucleus)Nuclear binding energy:1679.09698531 MeV (per nucleus)
7.73777413 MeV (average binding energy per nucleon)Separation energy:S_N = 6.728(8) MeV (first neutron)
S_P = 3.228(9) MeV (first proton)Half-life:22(5) μsDecay constant λ:31506.690025452 s^-1Specific activity α:8.743673979891 × 10⁺²⁵ Bq g^-1
2.363155129700 × 10⁺¹⁵ Ci g^-1Spin and parity:
(nuclear angular momentum)9/2-Year of discovery:1968

Radioactive Decay

Half-life T_½ = 22(5) μs respectively 2.2 × 10^-5 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²¹³At	100 %	8.469(4) MeV

Parent Nuclides

Direct parent isotope is: ²²¹Ac.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 130) and isobaric (same nucleon number A = 217) with Francium-217. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 130	Isobar A = 217
78	²⁰⁸Pt
79	²⁰⁹Au
80	²¹⁰Hg
81	²¹¹Tl	²¹⁷Tl
82	²¹²Pb	²¹⁷Pb
83	²¹³Bi	²¹⁷Bi
84	²¹⁴Po	²¹⁷Po
85	²¹⁵At	²¹⁷At
86	²¹⁶Rn	²¹⁷Rn
87	²¹⁷Fr	²¹⁷Fr
88	²¹⁸Ra	²¹⁷Ra
89	²¹⁹Ac	²¹⁷Ac
90	²²⁰Th	²¹⁷Th
91	²²¹Pa	²¹⁷Pa
92	²²²U	²¹⁷U
93	²²³Np

External data and identifiers

Adopted Levels, Gammas:NuDat 217Fr

Literature and References

[1] - R. L. Hahn, M. F. Roche, K. S Toth:
New neptunium isotopes, ²³⁰Np and ²²⁹Np.
In: Nuclear Physics A, 113, 1, (1968), DOI 10.1016/0375-9474(68)90894-4.

[2] - E. Rey-herme et al.:
Level structure of ²²¹Ac and ²¹⁷Fr from decay spectroscopy, and reflection asymmetry in ²²¹Ac.
In: Physical Review C, 108, 014304, (2023), DOI 10.1103/PhysRevC.108.014304.