Polonium-222

Properties and data of the isotope ²²²Po.

Contents

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

General data

Name of the isotope:Polonium-222; Po-222Symbol:²²²Po or 22284PoMass number A:222 (= number of nucleons)Atomic number Z:84 (= number of protons)Neutrons N:138Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.6428571428571 (= neutron-proton ratio)Neutron excess (N-Z):54Isotopic mass:222.02414(4) u (atomic weight of Polonium-222)Nuclide mass:221.9780647 u (calculated nuclear mass without electrons)Mass excess:22.48627 MeVMass defect:1.828921096 u (per nucleus)Nuclear binding energy:1703.6290274 MeV (per nucleus)
7.67400463 MeV (average binding energy per nucleon)Half-life:550(430) sDecay constant λ:0.0012602676010181 s^-1Specific activity α:3.418697754299 × 10⁺¹⁸ Bq g^-1
92397236.602697 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Year of discovery:2010

Radioactive Decay

Half-life T_½ = 550(430) s respectively 5.50 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^- ?

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 138) and isobaric (same nucleon number A = 222) with Polonium-222. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 138	Isobar A = 222
82	²²⁰Pb
83	²²¹Bi	²²²Bi
84	²²²Po	²²²Po
85	²²³At	²²²At
86	²²⁴Rn	²²²Rn
87	²²⁵Fr	²²²Fr
88	²²⁶Ra	²²²Ra
89	²²⁷Ac	²²²Ac
90	²²⁸Th	²²²Th
91	²²⁹Pa	²²²Pa
92	²³⁰U	²²²U
93	²³¹Np	²²²Np
94	²³²Pu
95	²³³Am
96	²³⁴Cm
97	²³⁵Bk