Francium-209

Properties and data of the isotope ²⁰⁹Fr.

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-209; Fr-209Symbol:²⁰⁹Fr or 20987FrMass number A:209 (= number of nucleons)Atomic number Z:87 (= number of protons)Neutrons N:122Isotopic mass:208.995953(16) u (atomic weight of Francium-209)Nuclide mass:208.9482324 u (calculated nuclear mass without electrons)Mass excess:-3.76976 MeVMass defect:1.741944536 u (per nucleus)Nuclear binding energy:1622.61088362 MeV (per nucleus)
7.76368844 MeV (average binding energy per nucleon)Separation energy:S_N = 9.175(19) MeV (first neutron)
S_P = 1.403(18) MeV (first proton)Half-life:50.5(7) sDecay constant λ:0.013725686743761 s^-1Specific activity α:3.973943219725 × 10⁺¹⁹ Bq g^-1
1074038708.034 Ci g^-1Spin and parity:
(nuclear angular momentum)9/2-Magnetic dipole moment:μ(μ_N) = + 3.95(8)Quadrupole moment Q:-0.24(2) barn (100 fm²)Nuclear g-factor:g_l = 0.87777777777778Charge radius:5.5799(176) femtometer fmYear of discovery:1964

Radioactive Decay

Half-life T_½ = 50.5(7) s respectively 5.05 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²⁰⁵At	89(3) %	6.777(4) MeV
EC/β⁺	²⁰⁹Rn	11(3) %	5.171(18) MeV

Parent Nuclides

Direct parent isotope is: ²¹³Ac.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 122) and isobaric (same nucleon number A = 209) with Francium-209. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

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