Polonium-212m

Properties and data of the isotope ²¹²Po.

Content

General data

Name of the isotope:Polonium-212m; Po-212mSymbol:²¹²Po or 21284PoMass number A:212 (= number of nucleons)Atomic number Z:84 (= number of protons)Neutrons N:128Isotopic mass:211.9888679(12) u (atomic weight of Polonium-212m)
Excitation energy: 2922(15) keVNuclide mass:211.9427926 u (calculated nuclear mass without electrons)Mass excess:-10.36948 MeVMass defect:1.777544036 u (per nucleus)Nuclear binding energy:1655.77160427 MeV (per nucleus)
7.81024342 MeV (average binding energy per nucleon)Half-life:45.1(6) sDecay constant λ:0.015369117085586 s^-1Specific activity α:4.386492321434 × 10⁺¹⁹ Bq g^-1
1185538465.2525 Ci g^-1Spin and parity:
(nuclear angular momentum)(18+)

Radioactive Decay

Half-life T_½ = 45.1(6) s respectively 4.51 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²⁰⁸Pb	99.93(2) %
Iso	²¹²Po	0.07(2) %

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
²¹²Po		0.299(2) μs	0+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 128) and isobaric (same nucleon number A = 212) with Polonium-212m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 128	Isobar A = 212
77	²⁰⁵Ir
78	²⁰⁶Pt
79	²⁰⁷Au
80	²⁰⁸Hg	²¹²Hg
81	²⁰⁹Tl	²¹²Tl
82	²¹⁰Pb	²¹²Pb
83	²¹¹Bi	²¹²Bi
84	²¹²Po	²¹²Po
85	²¹³At	²¹²At
86	²¹⁴Rn	²¹²Rn
87	²¹⁵Fr	²¹²Fr
88	²¹⁶Ra	²¹²Ra
89	²¹⁷Ac	²¹²Ac
90	²¹⁸Th	²¹²Th
91	²¹⁹Pa	²¹²Pa
92	²²⁰U
95	²²³Am