Francium-204

Properties and data of the isotope ²⁰⁴Fr.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

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

General data

Name of the isotope:Francium-204; Fr-204Symbol:²⁰⁴Fr or 20487FrMass number A:204 (= number of nucleons)Atomic number Z:87 (= number of protons)Neutrons N:117Isotopic mass:204.000652(26) u (atomic weight of Francium-204)Nuclide mass:203.9529314 u (calculated nuclear mass without electrons)Mass excess:0.60733 MeVMass defect:1.693920956 u (per nucleus)Nuclear binding energy:1577.87720699 MeV (per nucleus)
7.73469219 MeV (average binding energy per nucleon)Separation energy:S_N = 8.34(25) MeV (first neutron)
S_P = 0.53(3) MeV (first proton)Half-life:1.8(3) sDecay constant λ:0.38508176697775 s^-1Specific activity α:1.136772864379 × 10⁺²¹ Bq g^-1
30723590929.165 Ci g^-1Spin and parity:
(nuclear angular momentum)(3+)Year of discovery:1964

Radioactive Decay

Half-life T_½ = 1.8(3) s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²⁰⁰At	92(2) %	7.1703(24) MeV
EC/β⁺	²⁰⁴Rn	8(2) %	8.578(26) MeV

Parent Nuclides

Direct parent isotope is: ²⁰⁸Ac.

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
^204m1Fr	41(7) keV	ca. 1.6 s	(7+)
^204m2Fr	316(7) keV	0.8(2) s	(10-)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 117) and isobaric (same nucleon number A = 204) with Francium-204. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 117	Isobar A = 204
71	¹⁸⁸Lu
72	¹⁸⁹Hf
73	¹⁹⁰Ta
74	¹⁹¹W
75	¹⁹²Re
76	¹⁹³Os
77	¹⁹⁴Ir	²⁰⁴Ir
78	¹⁹⁵Pt	²⁰⁴Pt
79	¹⁹⁶Au	²⁰⁴Au
80	¹⁹⁷Hg	²⁰⁴Hg
81	¹⁹⁸Tl	²⁰⁴Tl
82	¹⁹⁹Pb	²⁰⁴Pb
83	²⁰⁰Bi	²⁰⁴Bi
84	²⁰¹Po	²⁰⁴Po
85	²⁰²At	²⁰⁴At
86	²⁰³Rn	²⁰⁴Rn
87	²⁰⁴Fr	²⁰⁴Fr
88	²⁰⁵Ra	²⁰⁴Ra
89	²⁰⁶Ac	²⁰⁴Ac
90	²⁰⁷Th