Cerium-121

Properties and data of the isotope ¹²¹Ce.

Contents

General data

Name of the isotope:Cerium-121; Ce-121Symbol:¹²¹Ce or 12158CeMass number A:121 (= number of nucleons)Atomic number Z:58 (= number of protons)Neutrons N:63Isotopic mass:120.94343(43) u (atomic weight of Cerium-121)Nuclide mass:120.9116146 u (calculated nuclear mass without electrons)Mass excess:-52.69462 MeVMass defect:1.056311564 u (per nucleus)Nuclear binding energy:983.947884 MeV (per nucleus)
8.13180069 MeV (average binding energy per nucleon)Separation energy:S_N = 11.16(64) MeV (first neutron)
S_P = 2.41(50) MeV (first proton)Half-life:1.1(1) sDecay constant λ:0.63013380050904 s^-1Specific activity α:3.162295422727 × 10⁺²¹ Bq g^-1
85467443857.495 Ci g^-1Spin and parity:
(nuclear angular momentum)(5/2)Year of discovery:1997

Radioactive Decay

Half-life T_½ = 1.1(1) s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC, β⁺	¹²¹La	> 99 %	9.5 (5) MeV
EC, p	¹²⁰Ba	< 1 %

Parent Nuclides

Direct parent isotope is: ¹²¹Pr.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 63) and isobaric (same nucleon number A = 121) with Cerium-121. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

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