Astatine-210

Properties and data of the isotope ²¹⁰At.

Content

General data

Name of the isotope:Astatine-210; At-210Symbol:²¹⁰At or 21085AtMass number A:210 (= number of nucleons)Atomic number Z:85 (= number of protons)Neutrons N:125Isotopic mass:209.987147(8) u (atomic weight of Astatine-210)Nuclide mass:209.9405233 u (calculated nuclear mass without electrons)Mass excess:-11.97249 MeVMass defect:1.76109522 u (per nucleus)Nuclear binding energy:1640.44963086 MeV (per nucleus)
7.81166491 MeV (average binding energy per nucleon)Separation energy:S_N = 7.161(9) MeV (first neutron)
S_P = 2.895(8) MeV (first proton)Half-life:8.1(4) hDecay constant λ:2.377047944307 × 10^-5 s^-1Specific activity α:6.849242847579 × 10⁺¹⁶ Bq g^-1
1851146.7155619 Ci g^-1Spin and parity:
(nuclear angular momentum)(5)+Year of discovery:1949

Radioactive Decay

Half-life T_½ = 8.1(4) h (hours) respectively 2.9160 × 10⁴ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²⁰⁶Bi	0.175(20) %	5.6312(10) MeV
EE/β⁺	²¹⁰Po	99.825(20) %	3.981(8) MeV

Parent Nuclides

Direct parent isotopes are: ²¹⁴Fr, ²¹⁰Rn.

Occurrence

Comparison of the natural Astatine isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):

	Atomic Mass m_a	Quantity	Half-life	Spin
Astatine Isotopic mixture	209.987146832 u	100 %
Isotope ²¹⁰At	209.987147(8) u	100 %	8.1(4) h	(5)+

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
^210m1At	2549.6(2) keV	0.482(6) μs	(15)-
^210m2At	4027.7(2) keV	5.66(7) μs	(19)+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 125) and isobaric (same nucleon number A = 210) with Astatine-210. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 125	Isobar A = 210
76	²⁰¹Os
77	²⁰²Ir
78	²⁰³Pt
79	²⁰⁴Au	²¹⁰Au
80	²⁰⁵Hg	²¹⁰Hg
81	²⁰⁶Tl	²¹⁰Tl
82	²⁰⁷Pb	²¹⁰Pb
83	²⁰⁸Bi	²¹⁰Bi
84	²⁰⁹Po	²¹⁰Po
85	²¹⁰At	²¹⁰At
86	²¹¹Rn	²¹⁰Rn
87	²¹²Fr	²¹⁰Fr
88	²¹³Ra	²¹⁰Ra
89	²¹⁴Ac	²¹⁰Ac
90	²¹⁵Th	²¹⁰Th
91	²¹⁶Pa
92	²¹⁷U