Actinium-215

Properties and data of the isotope ²¹⁵Ac.

Contents

Actinium-215 is a radioisotope of the chemical element actinium, which, in addition to element-specific 89 protons, has 126 neutrons in the atomic nucleus, resulting in the mass number 215. The very short-lived, only artificially producible, unstable and therefore radioactive nuclide has no practical significance; dealing with ²¹⁵Ac is for academic purposes only.

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

General data

Name of the isotope:Actinium-215; Ac-215Symbol:²¹⁵Ac or 21589AcMass number A:215 (= number of nucleons)Atomic number Z:89 (= number of protons)Neutrons N:126Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):1.4157303370787 (= neutron-proton ratio)Neutron excess (N-Z):37Isotopic mass:215.006474(13) u (atomic weight of Actinium-215)Nuclide mass:214.9576566 u (calculated nuclear mass without electrons)Mass excess:6.03049 MeVMass defect:1.781733264 u (per nucleus)Nuclear binding energy:1659.67384502 MeV (per nucleus)
7.71941323 MeV (average binding energy per nucleon)Separation energy:S_N = 8.485(20) MeV (first neutron)
S_P = 1.351(13) MeV (first proton)Half-life:0.17(1) sDecay constant λ:4.077336356235 s^-1Specific activity α:1.142060180027 × 10⁺²² Bq g^-1
308664913520.92 Ci g^-1Spin and parity:
(nuclear angular momentum)9/2-Magnetic dipole moment:μ(μ_N) = +4.14(6)Nuclear g-factor:g_l = 0.92Year of discovery:1968

Radioactive Decay

Half-life T_½ = 0.17(1) s respectively 1.7 × 10^-1 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²¹¹Fr	99.91(2) %	7.746(3) MeV
EC/β⁺	²¹⁵Ra	0.09(2) %	3.497(15) MeV

Parent Nuclides

Direct parent isotope is: ²¹⁹Pa.

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
^215m1Ac	1796.0(9) keV	185(30) ns	(21/2-)
^215m2Ac	2438+x keV	335(10) ns	(29/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 126) and isobaric (same nucleon number A = 215) with Actinium-215. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 126	Isobar A = 215
76	²⁰²Os
77	²⁰³Ir
78	²⁰⁴Pt
79	²⁰⁵Au
80	²⁰⁶Hg	²¹⁵Hg
81	²⁰⁷Tl	²¹⁵Tl
82	²⁰⁸Pb	²¹⁵Pb
83	²⁰⁹Bi	²¹⁵Bi
84	²¹⁰Po	²¹⁵Po
85	²¹¹At	²¹⁵At
86	²¹²Rn	²¹⁵Rn
87	²¹³Fr	²¹⁵Fr
88	²¹⁴Ra	²¹⁵Ra
89	²¹⁵Ac	²¹⁵Ac
90	²¹⁶Th	²¹⁵Th
91	²¹⁷Pa	²¹⁵Pa
92	²¹⁸U	²¹⁵U
93	²¹⁹Np