Samarium-128

Properties and data of the isotope ¹²⁸Sm.

Content

General data

Name of the isotope:Samarium-128; Sm-128Symbol:¹²⁸Sm or 12862SmMass number A:128 (= number of nucleons)Atomic number Z:62 (= number of protons)Neutrons N:66Isotopic mass:127.95808(54) u (atomic weight of Samarium-128)Nuclide mass:127.9240707 u (calculated nuclear mass without electrons)Mass excess:-39.04823 MeVMass defect:1.09895644 u (per nucleus)Nuclear binding energy:1023.67133012 MeV (per nucleus)
7.99743227 MeV (average binding energy per nucleon)Half-life:0.5 sDecay constant λ:1.3862943611199 s^-1Specific activity α:6.573590485039 × 10⁺²¹ Bq g^-1
177664607703.77 Ci g^-1Spin and parity:
(nuclear angular momentum)0+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 66) and isobaric (same nucleon number A = 128) with Samarium-128. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 66	Isobar A = 128
37	¹⁰³Rb
38	¹⁰⁴Sr
39	¹⁰⁵Y
40	¹⁰⁶Zr
41	¹⁰⁷Nb
42	¹⁰⁸Mo
43	¹⁰⁹Tc
44	¹¹⁰Ru
45	¹¹¹Rh
46	¹¹²Pd	¹²⁸Pd
47	¹¹³Ag	¹²⁸Ag
48	¹¹⁴Cd	¹²⁸Cd
49	¹¹⁵In	¹²⁸In
50	¹¹⁶Sn	¹²⁸Sn
51	¹¹⁷Sb	¹²⁸Sb
52	¹¹⁸Te	¹²⁸Te
53	¹¹⁹I	¹²⁸I
54	¹²⁰Xe	¹²⁸Xe
55	¹²¹Cs	¹²⁸Cs
56	¹²²Ba	¹²⁸Ba
57	¹²³La	¹²⁸La
58	¹²⁴Ce	¹²⁸Ce
59	¹²⁵Pr	¹²⁸Pr
60	¹²⁶Nd	¹²⁸Nd
61	¹²⁷Pm	¹²⁸Pm
62	¹²⁸Sm	¹²⁸Sm