Lanthanum-122

Properties and data of the isotope ¹²²La.

Contents

General data

Name of the isotope:Lanthanum-122; La-122Symbol:¹²²La or 12257LaMass number A:122 (= number of nucleons)Atomic number Z:57 (= number of protons)Neutrons N:65Isotopic mass:121.93071(32) u (atomic weight of Lanthanum-122)Nuclide mass:121.8994431 u (calculated nuclear mass without electrons)Mass excess:-64.54322 MeVMass defect:1.078536364 u (per nucleus)Nuclear binding energy:1004.65015185 MeV (per nucleus)
8.23483731 MeV (average binding energy per nucleon)Separation energy:S_N = 10.42(42) MeV (first neutron)
S_P = 1.09(33) MeV (first proton)Half-life:8.6(5) sDecay constant λ:0.080598509367435 s^-1Specific activity α:4.011368400922 × 10⁺²⁰ Bq g^-1
10841536218.709 Ci g^-1Spin and parity:
(nuclear angular momentum)Year of discovery:1984

Radioactive Decay

Half-life T_½ = 8.6(5) s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	¹²²Ba	100 %	10.07(30) MeV
EC, p	¹²¹Cs	?

Parent Nuclides

Direct parent isotope is: ¹²²Ce.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 65) and isobaric (same nucleon number A = 122) with Lanthanum-122. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 65	Isobar A = 122
36	¹⁰¹Kr
37	¹⁰²Rb
38	¹⁰³Sr
39	¹⁰⁴Y
40	¹⁰⁵Zr
41	¹⁰⁶Nb
42	¹⁰⁷Mo
43	¹⁰⁸Tc
44	¹⁰⁹Ru	¹²²Ru
45	¹¹⁰Rh	¹²²Rh
46	¹¹¹Pd	¹²²Pd
47	¹¹²Ag	¹²²Ag
48	¹¹³Cd	¹²²Cd
49	¹¹⁴In	¹²²In
50	¹¹⁵Sn	¹²²Sn
51	¹¹⁶Sb	¹²²Sb
52	¹¹⁷Te	¹²²Te
53	¹¹⁸I	¹²²I
54	¹¹⁹Xe	¹²²Xe
55	¹²⁰Cs	¹²²Cs
56	¹²¹Ba	¹²²Ba
57	¹²²La	¹²²La
58	¹²³Ce	¹²²Ce
59	¹²⁴Pr	¹²²Pr
60	¹²⁵Nd
61	¹²⁶Pm