Astatine-198m

Properties and data of the isotope ¹⁹⁸At.

Content

General data

Name of the isotope:Astatine-198m; At-198mSymbol:¹⁹⁸At or 19885AtMass number A:198 (= number of nucleons)Atomic number Z:85 (= number of protons)Neutrons N:113Isotopic mass:197.992792(6) u (atomic weight of Astatine-198m)
Excitation energy: 102+x keVNuclide mass:197.9461683 u (calculated nuclear mass without electrons)Mass excess:-6.71421 MeVMass defect:1.651471228 u (per nucleus)Nuclear binding energy:1538.33554005 MeV (per nucleus)
7.76937141 MeV (average binding energy per nucleon)Half-life:1.21(6) sDecay constant λ:0.57284890955367 s^-1Specific activity α:1.751155748626 × 10⁺²¹ Bq g^-1
47328533746.651 Ci g^-1Spin and parity:
(nuclear angular momentum)(10-)

Radioactive Decay

Half-life T_½ = 1.21(6) s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	¹⁹⁴Bi	84(16) %
EE/β⁺	¹⁹⁸Po	16(16) %

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
¹⁹⁸At		4.2(2) s	(3+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 113) and isobaric (same nucleon number A = 198) with Astatine-198m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 113	Isobar A = 198
70	¹⁸³Yb
71	¹⁸⁴Lu
72	¹⁸⁵Hf
73	¹⁸⁶Ta
74	¹⁸⁷W
75	¹⁸⁸Re	¹⁹⁸Re
76	¹⁸⁹Os	¹⁹⁸Os
77	¹⁹⁰Ir	¹⁹⁸Ir
78	¹⁹¹Pt	¹⁹⁸Pt
79	¹⁹²Au	¹⁹⁸Au
80	¹⁹³Hg	¹⁹⁸Hg
81	¹⁹⁴Tl	¹⁹⁸Tl
82	¹⁹⁵Pb	¹⁹⁸Pb
83	¹⁹⁶Bi	¹⁹⁸Bi
84	¹⁹⁷Po	¹⁹⁸Po
85	¹⁹⁸At	¹⁹⁸At
86	¹⁹⁹Rn	¹⁹⁸Rn
87	²⁰⁰Fr
88	²⁰¹Ra