Americium-240

Properties and data of the isotope ²⁴⁰Am.

Content

General data

Name of the isotope:Americium-240; Am-240Symbol:²⁴⁰Am or 24095AmMass number A:240 (= number of nucleons)Atomic number Z:95 (= number of protons)Neutrons N:145Isotopic mass:240.055298(15) u (atomic weight of Americium-240)Nuclide mass:240.0031901 u (calculated nuclear mass without electrons)Mass excess:51.50976 MeVMass defect:1.94449286 u (per nucleus)Nuclear binding energy:1811.28343213 MeV (per nucleus)
7.5470143 MeV (average binding energy per nucleon)Separation energy:S_N = 5.952(14) MeV (first neutron)
S_P = 4.367(14) MeV (first proton)Half-life:50.8(3) hDecay constant λ:3.790174871828 × 10^-6 s^-1Specific activity α:9.510402900809 × 10⁺¹⁵ Bq g^-1
257037.91623809 Ci g^-1Spin and parity:
(nuclear angular momentum)(3-)Year of discovery:1949

Radioactive Decay

Half-life T_½ = 50.8(3) h (hours) respectively 1.82880 × 10⁵ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²³⁶Np	trace	5.71(5) MeV
EE	²⁴⁰Pu	ca. 100 %	1.385(14) MeV

Parent Nuclides

Direct parent isotope is: ²⁴⁴Bk.

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
^240mAm	3000 keV	0.94(4) ms

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 145) and isobaric (same nucleon number A = 240) with Americium-240. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 145	Isobar A = 240
87	²³²Fr
88	²³³Ra
89	²³⁴Ac
90	²³⁵Th
91	²³⁶Pa	²⁴⁰Pa
92	²³⁷U	²⁴⁰U
93	²³⁸Np	²⁴⁰Np
94	²³⁹Pu	²⁴⁰Pu
95	²⁴⁰Am	²⁴⁰Am
96	²⁴¹Cm	²⁴⁰Cm
97	²⁴²Bk	²⁴⁰Bk
98	²⁴³Cf	²⁴⁰Cf
99	²⁴⁴Es	²⁴⁰Es
100	²⁴⁵Fm
101	²⁴⁶Md