Plutonium-238

Properties and data of the isotope ²³⁸Pu.

Content

Plutonium-238 is the radioisotope of the element plutonium, whose atomic nucleus has 144 neutrons in addition to the element-specific 94 protons, resulting in a mass number of 238: ²³⁸Pu.

Pu-238 is a fissile, alpha-emitting isotope that decays to Uranium-238 with a half-life of 87.7 years.

General data

Name of the isotope:Plutonium-238; Pu-238Symbol:²³⁸Pu or 23894PuMass number A:238 (= number of nucleons)Atomic number Z:94 (= number of protons)Neutrons N:144Isotopic mass:238.0495582(12) u (atomic weight of Plutonium-238)Nuclide mass:237.9979987 u (calculated nuclear mass without electrons)Mass excess:46.16317 MeVMass defect:1.933742712 u (per nucleus)Nuclear binding energy:1801.26973377 MeV (per nucleus)
7.56836023 MeV (average binding energy per nucleon)Separation energy:S_N = 6.9998(13) MeV (first neutron)
S_P = 5.9974(4) MeV (first proton)Half-life:87.7(1) aDecay constant λ:2.506226924684 × 10^-10 s^-1Specific activity α:634153427202.32 Bq g^-1
17.139281816279 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Charge radius:5.8535(378) femtometer fmYear of discovery:1940

Radioactive Decay

Half-life T_½ = 87.7(1) a respectively 2.7657 × 10⁹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²³⁴U	ca. 100 %	5.59327(19) MeV
SZ	^div	trace

Parent Nuclides

Direct parent isotopes are: ²³⁸Am, ²³⁸Np, ²⁴²Cm.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 144) and isobaric (same nucleon number A = 238) with Plutonium-238. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 144	Isobar A = 238
85	²²⁹At
86	²³⁰Rn
87	²³¹Fr
88	²³²Ra
89	²³³Ac
90	²³⁴Th	²³⁸Th
91	²³⁵Pa	²³⁸Pa
92	²³⁶U	²³⁸U
93	²³⁷Np	²³⁸Np
94	²³⁸Pu	²³⁸Pu
95	²³⁹Am	²³⁸Am
96	²⁴⁰Cm	²³⁸Cm
97	²⁴¹Bk	²³⁸Bk
98	²⁴²Cf	²³⁸Cf
99	²⁴³Es
100	²⁴⁴Fm
101	²⁴⁵Md