Lead-201

Properties and data of the isotope ²⁰¹Pb.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Lead-201 is a radioisotope of the chemical element lead, which has 119 neutrons in its atomic nucleus in addition to the element-specific 82 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 201. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ²⁰¹Pb is exclusively for academic purposes.

A report on the first observation of the nuclide was published in 1950 [1].

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

General data

Name of the isotope:Lead-201; Pb-201Symbol:²⁰¹Pb or 20182PbMass number A:201 (= number of nucleons)Atomic number Z:82 (= number of protons)Neutrons N:119Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.4512195121951 (= neutron-proton ratio)Neutron excess (N-Z):37Isotopic mass:200.972870(15) u (atomic weight of Lead-201)Nuclide mass:200.9278916 u (calculated nuclear mass without electrons)Mass excess:-25.27143 MeVMass defect:1.699907628 u (per nucleus)Nuclear binding energy:1583.45375604 MeV (per nucleus)
7.87787938 MeV (average binding energy per nucleon)Separation energy:S_N = 7.091(17) MeV (first neutron)
S_P = 5.513(15) MeV (first proton)Half-life:9.33(3) hDecay constant λ:2.063675064189 × 10^-5 s^-1Specific activity α:6.213870962843 × 10⁺¹⁶ Bq g^-1
1679424.5845524 Ci g^-1Spin and parity:
(nuclear angular momentum)5/2-Magnetic dipole moment:μ(μ_N) = + 0.6753(6)Quadrupole moment Q:- 0.01 barn (100 fm²)Nuclear g-factor:g_l = 0.27012Charge radius:5.4629(19) femtometer fmYear of discovery:1950

Radioactive Decay

Half-life T_½ = 9.33(3) h (hours) respectively 3.3588 × 10⁴ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β⁺	²⁰¹Tl	100 %	1.910(20) MeV

Parent Nuclides

Direct parent isotopes are: ²⁰¹Bi, ²⁰⁵Po.

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
^201m1Pb	629.1(3) keV	60.8(18) s	13/2+
^201m2Pb	2953(20) keV	508(5) ns	(29/2-)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 119) and isobaric (same nucleon number A = 201) with Lead-201. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 119	Isobar A = 201
73	¹⁹²Ta
74	¹⁹³W
75	¹⁹⁴Re
76	¹⁹⁵Os	²⁰¹Os
77	¹⁹⁶Ir	²⁰¹Ir
78	¹⁹⁷Pt	²⁰¹Pt
79	¹⁹⁸Au	²⁰¹Au
80	¹⁹⁹Hg	²⁰¹Hg
81	²⁰⁰Tl	²⁰¹Tl
82	²⁰¹Pb	²⁰¹Pb
83	²⁰²Bi	²⁰¹Bi
84	²⁰³Po	²⁰¹Po
85	²⁰⁴At	²⁰¹At
86	²⁰⁵Rn	²⁰¹Rn
87	²⁰⁶Fr	²⁰¹Fr
88	²⁰⁷Ra	²⁰¹Ra
89	²⁰⁸Ac
90	²⁰⁹Th
91	²¹⁰Pa