Erbium-158

Properties and data of the isotope ¹⁵⁸Er.

Content

General data

Name of the isotope:Erbium-158; Er-158Symbol:¹⁵⁸Er or 15868ErMass number A:158 (= number of nucleons)Atomic number Z:68 (= number of protons)Neutrons N:90Isotopic mass:157.929893(27) u (atomic weight of Erbium-158)Nuclide mass:157.8925929 u (calculated nuclear mass without electrons)Mass excess:-65.30425 MeVMass defect:1.382051616 u (per nucleus)Nuclear binding energy:1287.37278799 MeV (per nucleus)
8.14792904 MeV (average binding energy per nucleon)Separation energy:S_N = 9.96(4) MeV (first neutron)
S_P = 5.76(3) MeV (first proton)Half-life:2.29(6) hDecay constant λ:8.407898842308 × 10^-5 s^-1Specific activity α:3.225066953151 × 10⁺¹⁷ Bq g^-1
8716397.1706805 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Charge radius:5.1761(312) femtometer fmYear of discovery:1961

Radioactive Decay

Half-life T_½ = 2.29(6) h (hours) respectively 8.244 × 10³ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE	¹⁵⁸Ho	100 %	0.88(4) MeV

Parent Nuclides

Direct parent isotope is: ¹⁵⁸Tm.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 90) and isobaric (same nucleon number A = 158) with Erbium-158. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 90	Isobar A = 158
51	¹⁴¹Sb
52	¹⁴²Te
53	¹⁴³I
54	¹⁴⁴Xe
55	¹⁴⁵Cs
56	¹⁴⁶Ba
57	¹⁴⁷La
58	¹⁴⁸Ce
59	¹⁴⁹Pr	¹⁵⁸Pr
60	¹⁵⁰Nd	¹⁵⁸Nd
61	¹⁵¹Pm	¹⁵⁸Pm
62	¹⁵²Sm	¹⁵⁸Sm
63	¹⁵³Eu	¹⁵⁸Eu
64	¹⁵⁴Gd	¹⁵⁸Gd
65	¹⁵⁵Tb	¹⁵⁸Tb
66	¹⁵⁶Dy	¹⁵⁸Dy
67	¹⁵⁷Ho	¹⁵⁸Ho
68	¹⁵⁸Er	¹⁵⁸Er
69	¹⁵⁹Tm	¹⁵⁸Tm
70	¹⁶⁰Yb	¹⁵⁸Yb
71	¹⁶¹Lu	¹⁵⁸Lu
72	¹⁶²Hf	¹⁵⁸Hf
73	¹⁶³Ta	¹⁵⁸Ta
74	¹⁶⁴W	¹⁵⁸W
75	¹⁶⁵Re
76	¹⁶⁶Os
77	¹⁶⁷Ir
78	¹⁶⁸Pt