Actinium-219

Properties and data of the isotope ²¹⁹Ac.

Content

Actinium-219 is the very short-lived radioisotope of the element Actinium, whose atomic nucleus has 130 neutrons in addition to the element-specific 89 protons, resulting in a mass number of 219: ^{219 sup>Ac.}

General data

Name of the isotope:Actinium-219; Ac-219Symbol:²¹⁹Ac or 21989AcMass number A:219 (= number of nucleons)Atomic number Z:89 (= number of protons)Neutrons N:130Isotopic mass:219.01242(5) u (atomic weight of Actinium-219)Nuclide mass:218.9636026 u (calculated nuclear mass without electrons)Mass excess:11.56916 MeVMass defect:1.810446928 u (per nucleus)Nuclear binding energy:1686.42045075 MeV (per nucleus)
7.70055 MeV (average binding energy per nucleon)Separation energy:S_N = 7.35(7) MeV (first neutron)
S_P = 2.37(5) MeV (first proton)Half-life:11.8(15) μsDecay constant λ:58741.286488131 s^-1Specific activity α:1.615289048061 × 10⁺²⁶ Bq g^-1
4.365646075841 × 10⁺¹⁵ Ci g^-1Spin and parity:
(nuclear angular momentum)9/2-Year of discovery:1970

Radioactive Decay

Half-life T_½ = 11.8(15) μs respectively 1.18 × 10^-5 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²¹⁵Fr	100 %	8.83(5) MeV

Parent Nuclides

Direct parent isotope is: ²²³Pa.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 130) and isobaric (same nucleon number A = 219) with Actinium-219. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 130	Isobar A = 219
78	²⁰⁸Pt
79	²⁰⁹Au
80	²¹⁰Hg
81	²¹¹Tl
82	²¹²Pb	²¹⁹Pb
83	²¹³Bi	²¹⁹Bi
84	²¹⁴Po	²¹⁹Po
85	²¹⁵At	²¹⁹At
86	²¹⁶Rn	²¹⁹Rn
87	²¹⁷Fr	²¹⁹Fr
88	²¹⁸Ra	²¹⁹Ra
89	²¹⁹Ac	²¹⁹Ac
90	²²⁰Th	²¹⁹Th
91	²²¹Pa	²¹⁹Pa
92	²²²U	²¹⁹U