Radium-217

Properties and data of the isotope ²¹⁷Ra.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Radium-217 is a radioisotope of the chemical element radium, which has 129 neutrons in its atomic nucleus in addition to the element-specific 88 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 ²¹⁷Ra is exclusively for academic purposes and experimental research.

In 1970 a report appeared describing the first observation of the isotope radium-217. In the experiments presented there, 10.6-MeV/nucleon oxygen-16 ions from a heavy-ion accelerator struck a lead-208 target, producing, among other nuclei, thorium-221 in the reaction ²⁰⁸Pb(¹⁶O,3n)²²¹Th. Subsequent α decay gave rise to the nuclide Rn-217, which was unambiguously identified through spectra recorded with a Si(Au) detector [1].

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

General data

Name of the isotope:Radium-217; Ra-217Symbol:²¹⁷Ra or 21788RaMass number A:217 (= number of nucleons)Atomic number Z:88 (= number of protons)Neutrons N:129Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.4659090909091 (= neutron-proton ratio)Neutron excess (N-Z):41Isotopic mass:217.006323(8) u (atomic weight of Radium-217)Nuclide mass:216.958054 u (calculated nuclear mass without electrons)Mass excess:5.88984 MeVMass defect:1.80005398 u (per nucleus)Nuclear binding energy:1676.73948205 MeV (per nucleus)
7.72691006 MeV (average binding energy per nucleon)Separation energy:S_N = 5.473(11) MeV (first neutron)
S_P = 4.370(8) MeV (first proton)Half-life:1.6(2) μsDecay constant λ:433216.98784997 s^-1Specific activity α:1.20225517223 × 10⁺²⁷ Bq g^-1
3.249338303337 × 10⁺¹⁶ Ci g^-1Spin and parity:
(nuclear angular momentum)(9/2+)Year of discovery:1970

Radioactive Decay

Half-life T_½ = 1.6(2) μs respectively 1.6 × 10^-6 seconds s.

Decay mode	Daughter	Probability	Decay energy	Details	γ energy (intensity)
α	²¹³Rn	100 %	9.161(6) MeV	α: 8.992(8) MeV [100 %] recoil energy: 0.16576(15) MeV

Parent Nuclides

Direct parent isotopes are: ²²¹Th, ²¹⁷Ac.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 129) and isobaric (same nucleon number A = 217) with Radium-217. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 129	Isobar A = 217
78	²⁰⁷Pt
79	²⁰⁸Au
80	²⁰⁹Hg
81	²¹⁰Tl	²¹⁷Tl
82	²¹¹Pb	²¹⁷Pb
83	²¹²Bi	²¹⁷Bi
84	²¹³Po	²¹⁷Po
85	²¹⁴At	²¹⁷At
86	²¹⁵Rn	²¹⁷Rn
87	²¹⁶Fr	²¹⁷Fr
88	²¹⁷Ra	²¹⁷Ra
89	²¹⁸Ac	²¹⁷Ac
90	²¹⁹Th	²¹⁷Th
91	²²⁰Pa	²¹⁷Pa
92	²²¹U	²¹⁷U
93	²²²Np

External data and identifiers

Adopted Levels, Gammas:NuDat 217Ra

Literature and References

[1] - David F. Torgerson, Ronald D. Macfarlane:
Alpha decay of the ²²¹Th and ²²²Th decay chains.
In: Nuclear Physics A, 149, 3, (1970), DOI 10.1016/0375-9474(70)91053-5.