Radium-208m

Properties and data of the isotope ²⁰⁸Ra.

Content

General data

Name of the isotope:Radium-208m; Ra-208mSymbol:²⁰⁸Ra or 20888RaMass number A:208 (= number of nucleons)Atomic number Z:88 (= number of protons)Neutrons N:120Isotopic mass:208.001855(10) u (atomic weight of Radium-208m)
Excitation energy: 2147.4(4) KeVNuclide mass:207.953586 u (calculated nuclear mass without electrons)Mass excess:1.72792 MeVMass defect:1.726537736 u (per nucleus)Nuclear binding energy:1608.25954186 MeV (per nucleus)
7.73201703 MeV (average binding energy per nucleon)Half-life:270(21) nsDecay constant λ:2567211.7798516 s^-1Specific activity α:7.432745651709 × 10⁺²⁷ Bq g^-1
2.008850176137 × 10⁺¹⁷ Ci g^-1Spin and parity:
(nuclear angular momentum)(8+)

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
²⁰⁸Ra		1.3(2) s	0+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 120) and isobaric (same nucleon number A = 208) with Radium-208m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 120	Isobar A = 208
73	¹⁹³Ta
74	¹⁹⁴W
75	¹⁹⁵Re
76	¹⁹⁶Os
77	¹⁹⁷Ir
78	¹⁹⁸Pt	²⁰⁸Pt
79	¹⁹⁹Au	²⁰⁸Au
80	²⁰⁰Hg	²⁰⁸Hg
81	²⁰¹Tl	²⁰⁸Tl
82	²⁰²Pb	²⁰⁸Pb
83	²⁰³Bi	²⁰⁸Bi
84	²⁰⁴Po	²⁰⁸Po
85	²⁰⁵At	²⁰⁸At
86	²⁰⁶Rn	²⁰⁸Rn
87	²⁰⁷Fr	²⁰⁸Fr
88	²⁰⁸Ra	²⁰⁸Ra
89	²⁰⁹Ac	²⁰⁸Ac
90	²¹⁰Th	²⁰⁸Th