Astatine-212

Properties and data of the isotope ²¹²At.

Contents

General data

Name of the isotope:Astatine-212; At-212Symbol:²¹²At or 21285AtMass number A:212 (= number of nucleons)Atomic number Z:85 (= number of protons)Neutrons N:127Isotopic mass:211.9907372(26) u (atomic weight of Astatine-212)Nuclide mass:211.9441135 u (calculated nuclear mass without electrons)Mass excess:-8.62824 MeVMass defect:1.774834852 u (per nucleus)Nuclear binding energy:1653.24801563 MeV (per nucleus)
7.7983397 MeV (average binding energy per nucleon)Separation energy:S_N = 5.052(3) MeV (first neutron)
S_P = 3.4846(22) MeV (first proton)Half-life:314(2) msDecay constant λ:2.2074750973247 s^-1Specific activity α:6.300344066773 × 10⁺²¹ Bq g^-1
170279569372.25 Ci g^-1Spin and parity:
(nuclear angular momentum)(1-)Year of discovery:1954

Radioactive Decay

Half-life T_½ = 314(2) ms respectively 3.14 × 10^-1 seconds s.

Decay mode	Daughter	Probability	Decay energy
α	²⁰⁸Bi	> 99 %	7.8171(6) MeV
EC/β⁺	²¹²Po	<< 1 %	1.7413(26) MeV
β^-	²¹²Rn	<< 1 %	0,031(4) MeV

Parent Nuclides

Direct parent isotope is: ²¹⁶Fr.

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
^212m1At	223(7) keV	119(3) ms	(9-)
^212m2At	4771.6(11) keV	152(5) μs	(25-)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 127) and isobaric (same nucleon number A = 212) with Astatine-212. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 127	Isobar A = 212
76	²⁰³Os
77	²⁰⁴Ir
78	²⁰⁵Pt
79	²⁰⁶Au
80	²⁰⁷Hg	²¹²Hg
81	²⁰⁸Tl	²¹²Tl
82	²⁰⁹Pb	²¹²Pb
83	²¹⁰Bi	²¹²Bi
84	²¹¹Po	²¹²Po
85	²¹²At	²¹²At
86	²¹³Rn	²¹²Rn
87	²¹⁴Fr	²¹²Fr
88	²¹⁵Ra	²¹²Ra
89	²¹⁶Ac	²¹²Ac
90	²¹⁷Th	²¹²Th
91	²¹⁸Pa	²¹²Pa
92	²¹⁹U