Lead-181

Properties and data of the isotope ¹⁸¹Pb.

Contents

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

General data

Name of the isotope:Lead-181; Pb-181Symbol:¹⁸¹Pb or 18182PbMass number A:181 (= number of nucleons)Atomic number Z:82 (= number of protons)Neutrons N:99Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.2073170731707 (= neutron-proton ratio)Neutron excess (N-Z):17Isotopic mass:180.99665(8) u (atomic weight of Lead-181)Nuclide mass:180.9516716 u (calculated nuclear mass without electrons)Mass excess:-3.1205 MeVMass defect:1.502829308 u (per nucleus)Nuclear binding energy:1399.87648343 MeV (per nucleus)
7.73412422 MeV (average binding energy per nucleon)Separation energy:S_N = 9.25(8) MeV (first neutron)
S_P = 10.2(10) MeV (first proton)Half-life:45(20) msDecay constant λ:15.40327067911 s^-1Specific activity α:5.153370318518 × 10⁺²² Bq g^-1
1392802788788.8 Ci g^-1Spin and parity:
(nuclear angular momentum)(13/2+)Year of discovery:1989

Radioactive Decay

Half-life T_½ = 45(20) ms respectively 4.5 × 10^-2 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	¹⁷⁷Hg	98 %	7.240(7) MeV
β⁺	¹⁸¹Tl	2 %	9.25(8) MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 99) and isobaric (same nucleon number A = 181) with Lead-181. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 99	Isobar A = 181
57	¹⁵⁶La
58	¹⁵⁷Ce
59	¹⁵⁸Pr
60	¹⁵⁹Nd
61	¹⁶⁰Pm
62	¹⁶¹Sm
63	¹⁶²Eu
64	¹⁶³Gd
65	¹⁶⁴Tb
66	¹⁶⁵Dy
67	¹⁶⁶Ho
68	¹⁶⁷Er
69	¹⁶⁸Tm
70	¹⁶⁹Yb	¹⁸¹Yb
71	¹⁷⁰Lu	¹⁸¹Lu
72	¹⁷¹Hf	¹⁸¹Hf
73	¹⁷²Ta	¹⁸¹Ta
74	¹⁷³W	¹⁸¹W
75	¹⁷⁴Re	¹⁸¹Re
76	¹⁷⁵Os	¹⁸¹Os
77	¹⁷⁶Ir	¹⁸¹Ir
78	¹⁷⁷Pt	¹⁸¹Pt
79	¹⁷⁸Au	¹⁸¹Au
80	¹⁷⁹Hg	¹⁸¹Hg
81	¹⁸⁰Tl	¹⁸¹Tl
82	¹⁸¹Pb	¹⁸¹Pb