Lanthanum-125

Properties and data of the isotope ¹²⁵La.

Contents

General data

Name of the isotope:Lanthanum-125; La-125Symbol:¹²⁵La or 12557LaMass number A:125 (= number of nucleons)Atomic number Z:57 (= number of protons)Neutrons N:68Isotopic mass:124.920816(28) u (atomic weight of Lanthanum-125)Nuclide mass:124.8895491 u (calculated nuclear mass without electrons)Mass excess:-73.75942 MeVMass defect:1.114425112 u (per nucleus)Nuclear binding energy:1038.08030528 MeV (per nucleus)
8.30464244 MeV (average binding energy per nucleon)Separation energy:S_N = 11.57(6) MeV (first neutron)
S_P = 1.959(29) MeV (first proton)Half-life:64.8(12) sDecay constant λ:0.010696715749382 s^-1Specific activity α:5.194929756571 × 10⁺¹⁹ Bq g^-1
1404035069.3435 Ci g^-1Spin and parity:
(nuclear angular momentum)(3/2+)Year of discovery:1973

Radioactive Decay

Half-life T_½ = 64.8(12) s respectively 6.48 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	¹²⁵Ba	100 %	5.909(28) MeV

Parent Nuclides

Direct parent isotope is: ¹²⁵Ce.

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
^125mLa	107.00(10) keV	0.39(4) s

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 68) and isobaric (same nucleon number A = 125) with Lanthanum-125. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 68	Isobar A = 125
38	¹⁰⁶Sr
39	¹⁰⁷Y
40	¹⁰⁸Zr
41	¹⁰⁹Nb
42	¹¹⁰Mo
43	¹¹¹Tc
44	¹¹²Ru
45	¹¹³Rh	¹²⁵Rh
46	¹¹⁴Pd	¹²⁵Pd
47	¹¹⁵Ag	¹²⁵Ag
48	¹¹⁶Cd	¹²⁵Cd
49	¹¹⁷In	¹²⁵In
50	¹¹⁸Sn	¹²⁵Sn
51	¹¹⁹Sb	¹²⁵Sb
52	¹²⁰Te	¹²⁵Te
53	¹²¹I	¹²⁵I
54	¹²²Xe	¹²⁵Xe
55	¹²³Cs	¹²⁵Cs
56	¹²⁴Ba	¹²⁵Ba
57	¹²⁵La	¹²⁵La
58	¹²⁶Ce	¹²⁵Ce
59	¹²⁷Pr	¹²⁵Pr
60	¹²⁸Nd	¹²⁵Nd
61	¹²⁹Pm
62	¹³⁰Sm
63	¹³¹Eu