Lanthanum-120

Properties and data of the isotope ¹²⁰La.

Contents

General data

Name of the isotope:Lanthanum-120; La-120Symbol:¹²⁰La or 12057LaMass number A:120 (= number of nucleons)Atomic number Z:57 (= number of protons)Neutrons N:63Isotopic mass:119.93820(32) u (atomic weight of Lanthanum-120)Nuclide mass:119.9069331 u (calculated nuclear mass without electrons)Mass excess:-57.56633 MeVMass defect:1.053716532 u (per nucleus)Nuclear binding energy:981.53062726 MeV (per nucleus)
8.17942189 MeV (average binding energy per nucleon)Separation energy:S_N = 10.85(42) MeV (first neutron)
S_P = 0.27(36) MeV (first proton)Half-life:2.8(2) sDecay constant λ:0.24755256448569 s^-1Specific activity α:1.252770095438 × 10⁺²¹ Bq g^-1
33858651228.059 Ci g^-1Spin and parity:
(nuclear angular momentum)Year of discovery:1984

Radioactive Decay

Half-life T_½ = 2.8(2) s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	¹²⁰Ba	< 100 %	11.32(42) MeV
EC, p	¹¹⁹Cs	> 0 %

Parent Nuclides

Direct parent isotope is: ¹²⁰Ce.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 63) and isobaric (same nucleon number A = 120) with Lanthanum-120. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 63	Isobar A = 120
35	⁹⁸Br
36	⁹⁹Kr
37	¹⁰⁰Rb
38	¹⁰¹Sr
39	¹⁰²Y
40	¹⁰³Zr
41	¹⁰⁴Nb
42	¹⁰⁵Mo
43	¹⁰⁶Tc	¹²⁰Tc
44	¹⁰⁷Ru	¹²⁰Ru
45	¹⁰⁸Rh	¹²⁰Rh
46	¹⁰⁹Pd	¹²⁰Pd
47	¹¹⁰Ag	¹²⁰Ag
48	¹¹¹Cd	¹²⁰Cd
49	¹¹²In	¹²⁰In
50	¹¹³Sn	¹²⁰Sn
51	¹¹⁴Sb	¹²⁰Sb
52	¹¹⁵Te	¹²⁰Te
53	¹¹⁶I	¹²⁰I
54	¹¹⁷Xe	¹²⁰Xe
55	¹¹⁸Cs	¹²⁰Cs
56	¹¹⁹Ba	¹²⁰Ba
57	¹²⁰La	¹²⁰La
58	¹²¹Ce	¹²⁰Ce
59	¹²²Pr