Gold-209

Properties and data of the isotope ²⁰⁹Au.

Content

General data

Name of the isotope:Gold-209; Au-209Symbol:²⁰⁹Au or 20979AuMass number A:209 (= number of nucleons)Atomic number Z:79 (= number of protons)Neutrons N:130Isotopic mass:208.99727(43) u (atomic weight of Gold-209)Nuclide mass:208.9539369 u (calculated nuclear mass without electrons)Mass excess:-2.54298 MeVMass defect:1.747346608 u (per nucleus)Nuclear binding energy:1627.64288127 MeV (per nucleus)
7.78776498 MeV (average binding energy per nucleon)Separation energy:S_N = 4.51(50) MeV (first neutron)
S_P = 8.84(56) MeV (first proton)Half-life:300 nsDecay constant λ:2310490.6018665 s^-1Specific activity α:6.689471086538 × 10⁺²⁷ Bq g^-1
1.807965158523 × 10⁺¹⁷ Ci g^-1Spin and parity:
(nuclear angular momentum)(3/2+)Year of discovery:2010

Radioactive Decay

Half-life T_½ = 300 ns respectively 3.0 × 10^-7 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	²⁰⁹Hg	100 %	6.10(43) MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 130) and isobaric (same nucleon number A = 209) with Gold-209. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

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