Erbium-157

Properties and data of the isotope ¹⁵⁷Er.

Content

General data

Name of the isotope:Erbium-157; Er-157Symbol:¹⁵⁷Er or 15768ErMass number A:157 (= number of nucleons)Atomic number Z:68 (= number of protons)Neutrons N:89Isotopic mass:156.931923(28) u (atomic weight of Erbium-157)Nuclide mass:156.8946229 u (calculated nuclear mass without electrons)Mass excess:-63.41332 MeVMass defect:1.3713567 u (per nucleus)Nuclear binding energy:1277.41053791 MeV (per nucleus)
8.13637285 MeV (average binding energy per nucleon)Separation energy:S_N = 7.27(4) MeV (first neutron)
S_P = 5.22(7) MeV (first proton)Half-life:18.65(10) minDecay constant λ:0.00061943447771219 s^-1Specific activity α:2.39123184505 × 10⁺¹⁸ Bq g^-1
64627887.704162 Ci g^-1Spin and parity:
(nuclear angular momentum)3/2-Magnetic dipole moment:μ(μ_N) = - 0.412(3)Quadrupole moment Q:+ 0.92(2) barn (100 fm²)Nuclear g-factor:g_l = -0.27466666666667Year of discovery:1966

Radioactive Decay

Half-life T_½ = 18.65(10) min (minutes) respectively 1.119 × 10³ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE/β⁺	¹⁵⁷Ho	ca. 100 %	3.42(4) MeV

Parent Nuclides

Direct parent isotope is: ¹⁵⁷Tm.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 89) and isobaric (same nucleon number A = 157) with Erbium-157. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 89	Isobar A = 157
50	¹³⁹Sn
51	¹⁴⁰Sb
52	¹⁴¹Te
53	¹⁴²I
54	¹⁴³Xe
55	¹⁴⁴Cs
56	¹⁴⁵Ba
57	¹⁴⁶La
58	¹⁴⁷Ce	¹⁵⁷Ce
59	¹⁴⁸Pr	¹⁵⁷Pr
60	¹⁴⁹Nd	¹⁵⁷Nd
61	¹⁵⁰Pm	¹⁵⁷Pm
62	¹⁵¹Sm	¹⁵⁷Sm
63	¹⁵²Eu	¹⁵⁷Eu
64	¹⁵³Gd	¹⁵⁷Gd
65	¹⁵⁴Tb	¹⁵⁷Tb
66	¹⁵⁵Dy	¹⁵⁷Dy
67	¹⁵⁶Ho	¹⁵⁷Ho
68	¹⁵⁷Er	¹⁵⁷Er
69	¹⁵⁸Tm	¹⁵⁷Tm
70	¹⁵⁹Yb	¹⁵⁷Yb
71	¹⁶⁰Lu	¹⁵⁷Lu
72	¹⁶¹Hf	¹⁵⁷Hf
73	¹⁶²Ta	¹⁵⁷Ta
74	¹⁶³W	¹⁵⁷W
75	¹⁶⁴Re
76	¹⁶⁵Os
77	¹⁶⁶Ir
78	¹⁶⁷Pt