Astatine-203

Properties and data of the isotope ²⁰³At.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

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

General data

Name of the isotope:Astatine-203; At-203Symbol:²⁰³At or 20385AtMass number A:203 (= number of nucleons)Atomic number Z:85 (= number of protons)Neutrons N:118Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):1.3882352941176 (= neutron-proton ratio)Neutron excess (N-Z):33Isotopic mass:202.986943(11) u (atomic weight of Astatine-203)Nuclide mass:202.9403193 u (calculated nuclear mass without electrons)Mass excess:-12.16252 MeVMass defect:1.700644808 u (per nucleus)Nuclear binding energy:1584.14043478 MeV (per nucleus)
7.80364746 MeV (average binding energy per nucleon)Separation energy:S_N = 9.64(3) MeV (first neutron)
S_P = 1.51(14) MeV (first proton)Half-life:7.4(2) minDecay constant λ:0.0015611422985584 s^-1Specific activity α:4.65416773481 × 10⁺¹⁸ Bq g^-1
125788317.15714 Ci g^-1Spin and parity:
(nuclear angular momentum)9/2-Year of discovery:1951

Radioactive Decay

Half-life T_½ = 7.4(2) min (minutes) respectively 4.44 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	¹⁹⁹Bi	31(3) %	6.2101(8) MeV
EC/β⁺	²⁰³Po	69(3) %	5.148(14) MeV

Parent Nuclides

Direct parent isotope is: ²⁰⁷Fr.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 118) and isobaric (same nucleon number A = 203) with Astatine-203. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 118	Isobar A = 203
72	¹⁹⁰Hf
73	¹⁹¹Ta
74	¹⁹²W
75	¹⁹³Re
76	¹⁹⁴Os	²⁰³Os
77	¹⁹⁵Ir	²⁰³Ir
78	¹⁹⁶Pt	²⁰³Pt
79	¹⁹⁷Au	²⁰³Au
80	¹⁹⁸Hg	²⁰³Hg
81	¹⁹⁹Tl	²⁰³Tl
82	²⁰⁰Pb	²⁰³Pb
83	²⁰¹Bi	²⁰³Bi
84	²⁰²Po	²⁰³Po
85	²⁰³At	²⁰³At
86	²⁰⁴Rn	²⁰³Rn
87	²⁰⁵Fr	²⁰³Fr
88	²⁰⁶Ra	²⁰³Ra
89	²⁰⁷Ac	²⁰³Ac
90	²⁰⁸Th