Astatine-216

Properties and data of the isotope ²¹⁶At.

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-216; At-216Symbol:²¹⁶At or 21685AtMass number A:216 (= number of nucleons)Atomic number Z:85 (= number of protons)Neutrons N:131Isotopic mass:216.002423(4) u (atomic weight of Astatine-216)Nuclide mass:215.9557993 u (calculated nuclear mass without electrons)Mass excess:2.25701 MeVMass defect:1.797808716 u (per nucleus)Nuclear binding energy:1674.6480321 MeV (per nucleus)
7.75300015 MeV (average binding energy per nucleon)Separation energy:S_N = 4.559(8) MeV (first neutron)
S_P = 4.491(4) MeV (first proton)Half-life:0.30(3) msDecay constant λ:2310.4906018665 s^-1Specific activity α:6.441712898148 × 10⁺²⁴ Bq g^-1
1.74100348598 × 10⁺¹⁴ Ci g^-1Spin and parity:
(nuclear angular momentum)1-Year of discovery:1948

Radioactive Decay

Half-life T_½ = 0.30(3) ms respectively 3.0 × 10^-4 seconds s.

Decay mode	Daughter	Probability	Decay energy
α	²¹²Bi	> 99 %	7.950(3) MeV
EC	²¹⁶Po	<< 1 %	0.474(4) MeV
β^-	²¹⁶Rn	<< 1%	2,004(7) MeV

At-216 is a radioactive intermediate product of the thorium series starting from Thorium-232 (see there for the complete decay series).

Parent Nuclides

Direct parent isotope is: ²²⁰Fr.

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
^216mAt	413 keV	0.1 ms	(9-)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 131) and isobaric (same nucleon number A = 216) with Astatine-216. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 131	Isobar A = 216
79	²¹⁰Au
80	²¹¹Hg	²¹⁶Hg
81	²¹²Tl	²¹⁶Tl
82	²¹³Pb	²¹⁶Pb
83	²¹⁴Bi	²¹⁶Bi
84	²¹⁵Po	²¹⁶Po
85	²¹⁶At	²¹⁶At
86	²¹⁷Rn	²¹⁶Rn
87	²¹⁸Fr	²¹⁶Fr
88	²¹⁹Ra	²¹⁶Ra
89	²²⁰Ac	²¹⁶Ac
90	²²¹Th	²¹⁶Th
91	²²²Pa	²¹⁶Pa
92	²²³U	²¹⁶U
93	²²⁴Np