Gold-187

Properties and data of the isotope ¹⁸⁷Au.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Gold-187 is a radioisotope of the chemical element gold, which has 108 neutrons in its atomic nucleus in addition to the element-specific 79 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 187. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ¹⁸⁷Au is exclusively for academic purposes.

The first observation and identification of the nuclide was reported in 1955 [1].

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

General data

Name of the isotope:Gold-187; Au-187Symbol:¹⁸⁷Au or 18779AuMass number A:187 (= number of nucleons)Atomic number Z:79 (= number of protons)Neutrons N:108Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):1.3670886075949 (= neutron-proton ratio)Neutron excess (N-Z):29Isotopic mass:186.964542(24) u (atomic weight of Gold-187)Nuclide mass:186.9212089 u (calculated nuclear mass without electrons)Mass excess:-33.02891 MeVMass defect:1.589446456 u (per nucleus)Nuclear binding energy:1480.55983709 MeV (per nucleus)
7.91743228 MeV (average binding energy per nucleon)Separation energy:S_N = 9.385(31) MeV (first neutron)
S_P = 2.453(31) MeV (first proton)Half-life:8.3(2) minDecay constant λ:0.0013918618083533 s^-1Specific activity α:4.506445090037 × 10⁺¹⁸ Bq g^-1
121795813.24426 Ci g^-1Spin and parity:
(nuclear angular momentum)(1/2+)Magnetic dipole moment:μ(μ_N) = + 0.531(12)Nuclear g-factor:g_l = 1.062Charge radius:5.4018(57) femtometer fmYear of discovery:1955

Radioactive Decay

Half-life T_½ = 8.3(2) min (minutes) respectively 4.98 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α ?	¹⁸³Ir	trace ?	4.748(30) MeV
EC/β⁺	¹⁸⁷Pt	100 %	3.657(33) MeV

Parent Nuclides

Direct parent isotope is: ¹⁸⁷Hg.

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
^187mAu	120.33(14) keV	2.3(1) s	(9/2-)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 108) and isobaric (same nucleon number A = 187) with Gold-187. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 108	Isobar A = 187
66	¹⁷⁴Dy
67	¹⁷⁵Ho
68	¹⁷⁶Er
69	¹⁷⁷Tm
70	¹⁷⁸Yb
71	¹⁷⁹Lu	¹⁸⁷Lu
72	¹⁸⁰Hf	¹⁸⁷Hf
73	¹⁸¹Ta	¹⁸⁷Ta
74	¹⁸²W	¹⁸⁷W
75	¹⁸³Re	¹⁸⁷Re
76	¹⁸⁴Os	¹⁸⁷Os
77	¹⁸⁵Ir	¹⁸⁷Ir
78	¹⁸⁶Pt	¹⁸⁷Pt
79	¹⁸⁷Au	¹⁸⁷Au
80	¹⁸⁸Hg	¹⁸⁷Hg
81	¹⁸⁹Tl	¹⁸⁷Tl
82	¹⁹⁰Pb	¹⁸⁷Pb
83	¹⁹¹Bi	¹⁸⁷Bi
84	¹⁹²Po	¹⁸⁷Po
85	¹⁹³At
86	¹⁹⁴Rn