Bismuth-205

Properties and data of the isotope ²⁰⁵Bi.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Bismuth-205 is a radioisotope of the chemical element bismuth, which has 122 neutrons in its atomic nucleus in addition to the element-specific 83 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 205. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ²⁰⁵Bi is exclusively for academic purposes and experimental research.

In 1951 the nuclide was first described in the context of experiments on the production of polonium-isotopes, in which bismuth-205 was observed and identified as a decay product of Po-205 [1].

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

General data

Name of the isotope:Bismuth-205; Bi-205Symbol:²⁰⁵Bi or 20583BiMass number A:205 (= number of nucleons)Atomic number Z:83 (= number of protons)Neutrons N:122Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):1.4698795180723 (= neutron-proton ratio)Neutron excess (N-Z):39Isotopic mass:204.977385(5) u (atomic weight of Bismuth-205)Nuclide mass:204.9318581 u (calculated nuclear mass without electrons)Mass excess:-21.06574 MeVMass defect:1.729212408 u (per nucleus)Nuclear binding energy:1610.75098278 MeV (per nucleus)
7.85732187 MeV (average binding energy per nucleon)Separation energy:S_N = 8.491(10) MeV (first neutron)
S_P = 3.245(5) MeV (first proton)Half-life:14.91(7) dDecay constant λ:5.380641725041 × 10^-7 s^-1Specific activity α:1.588381489463 × 10⁺¹⁵ Bq g^-1
42929.229444954 Ci g^-1Spin and parity:
(nuclear angular momentum)9/2-Charge radius:5.5008(909) femtometer fmYear of discovery:1951

Radioactive Decay

Half-life T_½ = 14.91(7) d respectively 1.288224 × 10⁶ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	²⁰⁵Pb	100 %	2.705(5) MeV

Parent Nuclides

Direct parent isotopes are: ²⁰⁹At, ²⁰⁵Po.

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
^205m1Bi	1497.17(9) keV	7.9(7) μs	1/2+
^205m3Bi	2139.0(7)	220(25) ns	25/2+
^205m2Bi	2064.7(4) keV	100(6) ns	21/2+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 122) and isobaric (same nucleon number A = 205) with Bismuth-205. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 122	Isobar A = 205
74	¹⁹⁶W
75	¹⁹⁷Re
76	¹⁹⁸Os
77	¹⁹⁹Ir	²⁰⁵Ir
78	²⁰⁰Pt	²⁰⁵Pt
79	²⁰¹Au	²⁰⁵Au
80	²⁰²Hg	²⁰⁵Hg
81	²⁰³Tl	²⁰⁵Tl
82	²⁰⁴Pb	²⁰⁵Pb
83	²⁰⁵Bi	²⁰⁵Bi
84	²⁰⁶Po	²⁰⁵Po
85	²⁰⁷At	²⁰⁵At
86	²⁰⁸Rn	²⁰⁵Rn
87	²⁰⁹Fr	²⁰⁵Fr
88	²¹⁰Ra	²⁰⁵Ra
89	²¹¹Ac	²⁰⁵Ac
90	²¹²Th
91	²¹³Pa
92	²¹⁴U

External data and identifiers

Adopted Levels, Gammas:NuDat 205Bi

Literature and References

[1] - D. G. Karraker, D. H. Templeton:
Polonium Isotopes Produced with High Energy Particles.
In: Physical Review, 81, 510, (1951), DOI 10.1103/PhysRev.81.510.

[2] - V. Manov et al.:
Experimental study of the quadrupole collectivity of the low-lying states of ²⁰⁵Bi.
In: The European Physical Journal A, 60, 191, (2024), DOI 10.1140/epja/s10050-024-01418-z.