Polonium-218

Properties and data of the isotope ²¹⁸Po.

Contents

Polonium-218 is the radioisotope of the element polonium, whose atomic nucleus has 134 neutrons in addition to the element-specific 84 protons, resulting in a mass number of 218.

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

General data

Name of the isotope:Polonium-218; Po-218Other names:Radium ASymbol:²¹⁸Po or 21884PoMass number A:218 (= number of nucleons)Atomic number Z:84 (= number of protons)Neutrons N:134Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.5952380952381 (= neutron-proton ratio)Neutron excess (N-Z):50Isotopic mass:218.0089712(21) u (atomic weight of Polonium-218)Nuclide mass:217.9628959 u (calculated nuclear mass without electrons)Mass excess:8.35662 MeVMass defect:1.809430232 u (per nucleus)Nuclear binding energy:1685.47340453 MeV (per nucleus)
7.73152938 MeV (average binding energy per nucleon)Separation energy:S_N = 5.598(7) MeV (first neutron)
S_P = 7.662(18) MeV (first proton)Half-life:3.097(12) minDecay constant λ:0.0037302076232911 s^-1Specific activity α:1.030451180929 × 10⁺¹⁹ Bq g^-1
278500319.17022 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Charge radius:5.6558(173) femtometer fmYear of discovery:1904

Radioactive Decay

Half-life T_½ = 3.097(12) min (minutes) respectively 1.85820 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²¹⁴Pb	99.980(2) %	6.11475(9) MeV
β^-	²¹⁸At	0.020(2) %	0.256(12) MeV

Parent Nuclides

Direct parent isotopes are: ²²²Rn, ²¹⁸Bi.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 134) and isobaric (same nucleon number A = 218) with Polonium-218. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 134	Isobar A = 218
80	²¹⁴Hg
81	²¹⁵Tl
82	²¹⁶Pb	²¹⁸Pb
83	²¹⁷Bi	²¹⁸Bi
84	²¹⁸Po	²¹⁸Po
85	²¹⁹At	²¹⁸At
86	²²⁰Rn	²¹⁸Rn
87	²²¹Fr	²¹⁸Fr
88	²²²Ra	²¹⁸Ra
89	²²³Ac	²¹⁸Ac
90	²²⁴Th	²¹⁸Th
91	²²⁵Pa	²¹⁸Pa
92	²²⁶U	²¹⁸U
93	²²⁷Np
94	²²⁸Pu
95	²²⁹Am