Americium-235

Properties and data of the isotope ²³⁵Am.

Content

Americium-235 is the artificial radioisotope of the element Americium, whose atomic nucleus has 140 neutrons in addition to the element-specific 95 protons, resulting in a mass number of 235: ²³⁵Am.

General data

Name of the isotope:Americium-235; Am-235Symbol:²³⁵Am or 23595AmMass number A:235 (= number of nucleons)Atomic number Z:95 (= number of protons)Neutrons N:140Isotopic mass:235.04791(6) u (atomic weight of Americium-235)Nuclide mass:234.9958021 u (calculated nuclear mass without electrons)Mass excess:44.62788 MeVMass defect:1.90855628 u (per nucleus)Nuclear binding energy:1777.80872348 MeV (per nucleus)
7.5651435 MeV (average binding energy per nucleon)Separation energy:S_N = 7.91(17) MeV (first neutron)
S_P = 3.01(5) MeV (first proton)Half-life:10.3(6) minDecay constant λ:0.0011215973795468 s^-1Specific activity α:2.874220173517 × 10⁺¹⁸ Bq g^-1
77681626.311295 Ci g^-1Spin and parity:
(nuclear angular momentum)5/2-Year of discovery:1996

Radioactive Decay

Half-life T_½ = 10.3(6) min (minutes) respectively 6.18 × 10² seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²³¹Np	0.40(5) %	6.576(13) MeV
ε	²³⁵Pu	99.60(5) %	2.44(6) MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 140) and isobaric (same nucleon number A = 235) with Americium-235. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 140	Isobar A = 235
83	²²³Bi
84	²²⁴Po
85	²²⁵At
86	²²⁶Rn
87	²²⁷Fr
88	²²⁸Ra
89	²²⁹Ac	²³⁵Ac
90	²³⁰Th	²³⁵Th
91	²³¹Pa	²³⁵Pa
92	²³²U	²³⁵U
93	²³³Np	²³⁵Np
94	²³⁴Pu	²³⁵Pu
95	²³⁵Am	²³⁵Am
96	²³⁶Cm	²³⁵Cm
97	²³⁷Bk	²³⁵Bk
98	²³⁸Cf