Lead-185m

Properties and data of the isotope ^185mPb.

Contents

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

General data

Name of the isotope:Lead-185m; Pb-185mSymbol:^185mPb or 185m82PbMass number A:185 (= number of nucleons)Atomic number Z:82 (= number of protons)Neutrons N:103Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.2560975609756 (= neutron-proton ratio)Neutron excess (N-Z):21Excitation energy:+x keVIsotopic mass:184.987610(17) u (atomic weight of Lead-185m)Nuclide mass:184.9426316 u (calculated nuclear mass without electrons)Mass excess:-11.54121 MeVMass defect:1.546528972 u (per nucleus)Nuclear binding energy:1440.58245824 MeV (per nucleus)
7.78693221 MeV (average binding energy per nucleon)Half-life:4.3(2) sDecay constant λ:0.16119701873487 s^-1Specific activity α:5.27582148382 × 10⁺²⁰ Bq g^-1
14258976983.303 Ci g^-1Spin and parity:
(nuclear angular momentum)13/2+Magnetic dipole moment:μ(μ_N) = - 1.19(3)Nuclear g-factor:g_l = -0.18307692307692

Radioactive Decay

Half-life T_½ = 4.3(2) s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	¹⁸¹Hg	50(25) %
β⁺	¹⁸⁵Tl	?

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
¹⁸⁵Pb		6.3(4) s	3/2-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 103) and isobaric (same nucleon number A = 185) with Lead-185m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 103	Isobar A = 185
60	¹⁶³Nd
62	¹⁶⁵Sm
63	¹⁶⁶Eu
64	¹⁶⁷Gd
65	¹⁶⁸Tb
66	¹⁶⁹Dy
67	¹⁷⁰Ho
68	¹⁷¹Er
69	¹⁷²Tm
70	¹⁷³Yb	¹⁸⁵Yb
71	¹⁷⁴Lu	¹⁸⁵Lu
72	¹⁷⁵Hf	¹⁸⁵Hf
73	¹⁷⁶Ta	¹⁸⁵Ta
74	¹⁷⁷W	¹⁸⁵W
75	¹⁷⁸Re	¹⁸⁵Re
76	¹⁷⁹Os	¹⁸⁵Os
77	¹⁸⁰Ir	¹⁸⁵Ir
78	¹⁸¹Pt	¹⁸⁵Pt
79	¹⁸²Au	¹⁸⁵Au
80	¹⁸³Hg	¹⁸⁵Hg
81	¹⁸⁴Tl	¹⁸⁵Tl
82	¹⁸⁵Pb	¹⁸⁵Pb
83	¹⁸⁶Bi	¹⁸⁵Bi
84	¹⁸⁷Po
85	¹⁸⁸At