Polonium-208

Properties and data of the isotope ²⁰⁸Po.

Contents

General data

Name of the isotope:Polonium-208; Po-208Symbol:²⁰⁸Po or 20884PoMass number A:208 (= number of nucleons)Atomic number Z:84 (= number of protons)Neutrons N:124Isotopic mass:207.9812456(19) u (atomic weight of Polonium-208)Nuclide mass:207.9351703 u (calculated nuclear mass without electrons)Mass excess:-17.46961 MeVMass defect:1.750506672 u (per nucleus)Nuclear binding energy:1630.58646193 MeV (per nucleus)
7.83935799 MeV (average binding energy per nucleon)Separation energy:S_N = 8.395(7) MeV (first neutron)
S_P = 4.7039(25) MeV (first proton)Half-life:2.898(2) aDecay constant λ:7.584386787332 × 10^-9 s^-1Specific activity α:22064852932154 Bq g^-1
596.3473765447 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Charge radius:5.5584(176) femtometer fmYear of discovery:1947

Radioactive Decay

Half-life T_½ = 2.898(2) a respectively 9.1391328 × 10⁷ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²⁰⁴Pb	99.9960(4) %	5.2154(13) MeV
EC/β⁺	²⁰⁸Bi	0.0040(4) %	1.4006(29) MeV

Parent Nuclides

Direct parent isotopes are: ²¹²Rn, ²⁰⁸At.

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
^208mPo	2528.22(4)	350(20) ns	8+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 124) and isobaric (same nucleon number A = 208) with Polonium-208. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 124	Isobar A = 208
75	¹⁹⁹Re
76	²⁰⁰Os
77	²⁰¹Ir
78	²⁰²Pt	²⁰⁸Pt
79	²⁰³Au	²⁰⁸Au
80	²⁰⁴Hg	²⁰⁸Hg
81	²⁰⁵Tl	²⁰⁸Tl
82	²⁰⁶Pb	²⁰⁸Pb
83	²⁰⁷Bi	²⁰⁸Bi
84	²⁰⁸Po	²⁰⁸Po
85	²⁰⁹At	²⁰⁸At
86	²¹⁰Rn	²⁰⁸Rn
87	²¹¹Fr	²⁰⁸Fr
88	²¹²Ra	²⁰⁸Ra
89	²¹³Ac	²⁰⁸Ac
90	²¹⁴Th	²⁰⁸Th
91	²¹⁵Pa
92	²¹⁶U