See also: List of individual Astatine isotopes (and general data sources).
General data
Name of the isotope:Astatine-200m2; At-200m2Symbol:200m2At or 200m285AtMass number A:200 (= number of nucleons)Atomic number Z:85 (= number of protons)Neutrons N:115Nucleon pairing (Z - N):odd - oddNuclear ratio (N/Z ratio):1.3529411764706 (= neutron-proton ratio)Neutron excess (N-Z):30Excitation energy:343.8(29) keVIsotopic mass:199.990351(26) u (atomic weight of Astatine-200m2)Nuclide mass:199.9437273 u (calculated nuclear mass without electrons)Mass excess:-8.98799 MeVMass defect:1.67124206 u (per nucleus)Nuclear binding energy:1556.75195144 MeV (per nucleus) 7.78375976 MeV (average binding energy per nucleon)Half-life:6.3(5) sDecay constant λ:0.11002336199364 s-1Specific activity α:3.313040701719 × 10+20 Bq g-1 8954164058.7011 Ci g-1Spin and parity: (nuclear angular momentum)(10-)Magnetic dipole moment:μ(μN) = 2.69(11)Quadrupole moment Q:+0.5(4) barn (100 fm2)Nuclear g-factor:gl = 0.269Year of discovery:1967
Radioactive Decay
Half-life T½ = 6.3(5) s.
Decay mode
Daughter
Probability
Decay energy
γ energy (intensity)
α
196Bi
10.5(3) %
Iso
200At
89.5(3) %
Nuclear Isomers
Nuclear isomers or excited states with the activation energy in keV related to the ground state.
The following table shows the atomic nuclei that are isotonic (same neutron number N = 115) and isobaric (same nucleon number A = 200) with Astatine-200m2. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
