Polonium-199

Properties and data of the isotope ¹⁹⁹Po.

Contents

General data

Name of the isotope:Polonium-199; Po-199Symbol:¹⁹⁹Po or 19984PoMass number A:199 (= number of nucleons)Atomic number Z:84 (= number of protons)Neutrons N:115Isotopic mass:198.983673(19) u (atomic weight of Polonium-199)Nuclide mass:198.9375977 u (calculated nuclear mass without electrons)Mass excess:-15.2085 MeVMass defect:1.670095028 u (per nucleus)Nuclear binding energy:1555.68349801 MeV (per nucleus)
7.81750502 MeV (average binding energy per nucleon)Separation energy:S_N = 7.806(25) MeV (first neutron)
S_P = 3.13(3) MeV (first proton)Half-life:5.47(15) minDecay constant λ:0.0021119658152344 s^-1Specific activity α:6.423512944804 × 10⁺¹⁸ Bq g^-1
173608457.96769 Ci g^-1Spin and parity:
(nuclear angular momentum)(3/2-)Magnetic dipole moment:μ(μ_N) = -0.912(65)Quadrupole moment Q:-0.27(12) barn (100 fm²)Nuclear g-factor:g_l = -0.608Year of discovery:1965

Radioactive Decay

Half-life T_½ = 5.47(15) min (minutes) respectively 3.282 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	¹⁹⁵Pb	7.5(3) %	6.0743(19) MeV
EC/β⁺	¹⁹⁹Bi	92.5(3) %	5.589(21) MeV

Parent Nuclides

Direct parent isotope is: ²⁰³Rn.

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
^199mPo	310(2) keV	4.17(5) min	(13/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 115) and isobaric (same nucleon number A = 199) with Polonium-199. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 115	Isobar A = 199
70	¹⁸⁵Yb
71	¹⁸⁶Lu
72	¹⁸⁷Hf
73	¹⁸⁸Ta
74	¹⁸⁹W
75	¹⁹⁰Re	¹⁹⁹Re
76	¹⁹¹Os	¹⁹⁹Os
77	¹⁹²Ir	¹⁹⁹Ir
78	¹⁹³Pt	¹⁹⁹Pt
79	¹⁹⁴Au	¹⁹⁹Au
80	¹⁹⁵Hg	¹⁹⁹Hg
81	¹⁹⁶Tl	¹⁹⁹Tl
82	¹⁹⁷Pb	¹⁹⁹Pb
83	¹⁹⁸Bi	¹⁹⁹Bi
84	¹⁹⁹Po	¹⁹⁹Po
85	²⁰⁰At	¹⁹⁹At
86	²⁰¹Rn	¹⁹⁹Rn
87	²⁰²Fr	¹⁹⁹Fr
88	²⁰³Ra
89	²⁰⁴Ac