Americium-242

Properties and data of the isotope ²⁴²Am.

Contents

General data

Name of the isotope:Americium-242; Am-242Symbol:²⁴²Am or 24295AmMass number A:242 (= number of nucleons)Atomic number Z:95 (= number of protons)Neutrons N:147Isotopic mass:242.0595474(12) u (atomic weight of Americium-242)Nuclide mass:242.0074395 u (calculated nuclear mass without electrons)Mass excess:55.46805 MeVMass defect:1.957573292 u (per nucleus)Nuclear binding energy:1823.46777606 MeV (per nucleus)
7.53499081 MeV (average binding energy per nucleon)Separation energy:S_N = 5.53764(19) MeV (first neutron)
S_P = 4.77607(19) MeV (first proton)Half-life:16.02(2) hDecay constant λ:1.201878174087 × 10^-5 s^-1Specific activity α:2.990859363983 × 10⁺¹⁶ Bq g^-1
808340.36864424 Ci g^-1Spin and parity:
(nuclear angular momentum)1-Magnetic dipole moment:μ(μ_N) = + 0.3879(15)Quadrupole moment Q:-2.40(70) barn (100 fm²)Nuclear g-factor:g_l = 0.3879Year of discovery:1949

Radioactive Decay

Half-life T_½ = 16.02(2) h (hours) respectively 5.7672 × 10⁴ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	²⁴²Cm	82.7(3) %	0.663(4) MeV
EC	²⁴²Pu	17.3(3) %	0.751(17) MeV

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
^242m1Am	48.60(5) keV	141(2) a	5-
^242m2Am	2200(80) keV	14.0(10) ms	(2+,3-)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 147) and isobaric (same nucleon number A = 242) with Americium-242. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 147	Isobar A = 242
89	²³⁶Ac
90	²³⁷Th
91	²³⁸Pa
92	²³⁹U	²⁴²U
93	²⁴⁰Np	²⁴²Np
94	²⁴¹Pu	²⁴²Pu
95	²⁴²Am	²⁴²Am
96	²⁴³Cm	²⁴²Cm
97	²⁴⁴Bk	²⁴²Bk
98	²⁴⁵Cf	²⁴²Cf
99	²⁴⁶Es	²⁴²Es
100	²⁴⁷Fm	²⁴²Fm
101	²⁴⁸Md