Lanthanum-125m

Properties and data of the isotope ¹²⁵La.

Content

General data

Name of the isotope:Lanthanum-125m; La-125mSymbol: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-125m)
Excitation energy: 107.00(10) keVNuclide 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)Half-life:0.39(4) sDecay constant λ:1.7773004629742 s^-1Specific activity α:8.631575595533 × 10⁺²¹ Bq g^-1
233285826906.31 Ci g^-1Spin and parity:
(nuclear angular momentum)

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
¹²⁵La		64.8(12) s	(3/2+)

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-125m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	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