Lanthanum-126

Properties and data of the isotope ¹²⁶La.

Contents

General data

Name of the isotope:Lanthanum-126; La-126Symbol:¹²⁶La or 12657LaMass number A:126 (= number of nucleons)Atomic number Z:57 (= number of protons)Neutrons N:69Isotopic mass:125.91951(10) u (atomic weight of Lanthanum-126)Nuclide mass:125.8882431 u (calculated nuclear mass without electrons)Mass excess:-74.97595 MeVMass defect:1.124396028 u (per nucleus)Nuclear binding energy:1047.36815371 MeV (per nucleus)
8.31244566 MeV (average binding energy per nucleon)Separation energy:S_N = 9.29(9) MeV (first neutron)
S_P = 2.59(9) MeV (first proton)Half-life:54(2) sDecay constant λ:0.012836058899258 s^-1Specific activity α:6.184044382222 × 10⁺¹⁹ Bq g^-1
1671363346.5465 Ci g^-1Spin and parity:
(nuclear angular momentum)(5+)Year of discovery:1961

Radioactive Decay

Half-life T_½ = 54(2) s respectively 5.4 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	¹²⁶Ba	?	7.79(9) MeV

Parent Nuclides

Direct parent isotope is: ¹²⁶Ce.

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
^126mLa	+z keV	50 s

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 69) and isobaric (same nucleon number A = 126) with Lanthanum-126. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 69	Isobar A = 126
38	¹⁰⁷Sr
39	¹⁰⁸Y
40	¹⁰⁹Zr
41	¹¹⁰Nb
42	¹¹¹Mo
43	¹¹²Tc
44	¹¹³Ru
45	¹¹⁴Rh	¹²⁶Rh
46	¹¹⁵Pd	¹²⁶Pd
47	¹¹⁶Ag	¹²⁶Ag
48	¹¹⁷Cd	¹²⁶Cd
49	¹¹⁸In	¹²⁶In
50	¹¹⁹Sn	¹²⁶Sn
51	¹²⁰Sb	¹²⁶Sb
52	¹²¹Te	¹²⁶Te
53	¹²²I	¹²⁶I
54	¹²³Xe	¹²⁶Xe
55	¹²⁴Cs	¹²⁶Cs
56	¹²⁵Ba	¹²⁶Ba
57	¹²⁶La	¹²⁶La
58	¹²⁷Ce	¹²⁶Ce
59	¹²⁸Pr	¹²⁶Pr
60	¹²⁹Nd	¹²⁶Nd
61	¹³⁰Pm	¹²⁶Pm
62	¹³¹Sm
63	¹³²Eu