Polonium-189

Properties and data of the isotope ¹⁸⁹Po.

Contents

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

General data

Name of the isotope:Polonium-189; Po-189Symbol:¹⁸⁹Po or 18984PoMass number A:189 (= number of nucleons)Atomic number Z:84 (= number of protons)Neutrons N:105Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.25 (= neutron-proton ratio)Neutron excess (N-Z):21Isotopic mass:188.998473(24) u (atomic weight of Polonium-189)Nuclide mass:188.9523977 u (calculated nuclear mass without electrons)Mass excess:-1.42239 MeVMass defect:1.568645868 u (per nucleus)Nuclear binding energy:1461.18421417 MeV (per nucleus)
7.73113341 MeV (average binding energy per nucleon)Separation energy:S_N = 8.89(3) MeV (first neutron)
S_P = 1.516(25) MeV (first proton)Half-life:3.5(5) msDecay constant λ:198.04205158856 s^-1Specific activity α:6.343814525835 × 10⁺²³ Bq g^-1
17145444664421 Ci g^-1Spin and parity:
(nuclear angular momentum)(5/2-)Year of discovery:1999

Radioactive Decay

Half-life T_½ = 3.5(5) ms respectively 3.5 × 10^-3 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	¹⁸⁵Pb	~100 %	7.694(15) MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 105) and isobaric (same nucleon number A = 189) with Polonium-189. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 105	Isobar A = 189
63	¹⁶⁸Eu
64	¹⁶⁹Gd
65	¹⁷⁰Tb
66	¹⁷¹Dy
67	¹⁷²Ho
68	¹⁷³Er
69	¹⁷⁴Tm
70	¹⁷⁵Yb
71	¹⁷⁶Lu
72	¹⁷⁷Hf	¹⁸⁹Hf
73	¹⁷⁸Ta	¹⁸⁹Ta
74	¹⁷⁹W	¹⁸⁹W
75	¹⁸⁰Re	¹⁸⁹Re
76	¹⁸¹Os	¹⁸⁹Os
77	¹⁸²Ir	¹⁸⁹Ir
78	¹⁸³Pt	¹⁸⁹Pt
79	¹⁸⁴Au	¹⁸⁹Au
80	¹⁸⁵Hg	¹⁸⁹Hg
81	¹⁸⁶Tl	¹⁸⁹Tl
82	¹⁸⁷Pb	¹⁸⁹Pb
83	¹⁸⁸Bi	¹⁸⁹Bi
84	¹⁸⁹Po	¹⁸⁹Po
85	¹⁹⁰At	¹⁸⁹At