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Tellurium-121

Properties and data of the isotope 121Te.


Contents

Tellurium-121 is a radioisotope of the chemical element tellurium which, in addition to the element-specific 52 protons, has 69 neutrons in the atomic nucleus, resulting in the mass number 121. The very short-lived, only artificially producible, unstable and therefore radioactive nuclide has no practical significance; dealing with 121Te is for academic purposes only.

The isotope is one of the few atomic nuclei in which some metastable nuclear isomers have longer half-lives.

See also: list of Tellurium isotopes.

 

General data

Name of the isotope:Tellurium-121; Te-121Symbol:121Te or 12152TeMass number A:121 (= number of nucleons)Atomic number Z:52 (= number of protons)Neutrons N:69Isotopic mass:120.904945(28) u (atomic weight of Tellurium-121)Nuclide mass:120.8764206 u (calculated nuclear mass without electrons)Mass excess:-88.54316 MeVMass defect:1.099835868 u (per nucleus)Nuclear binding energy:1024.49051203 MeV (per nucleus)
8.46686374 MeV (average binding energy per nucleon)
Separation energy:SN = 7.252(26) MeV (first neutron)
SP = 7.415(27) MeV (first proton)
Half-life:19.17(4) dDecay constant λ:4.184943563920 × 10-7 s-1Specific activity α:2.100193302734 × 10+15 Bq g-1
56761.981154995 Ci g-1
Spin and parity:
(nuclear angular momentum)
1/2+Year of discovery:1939

 

Radioactive Decay

Half-life T½ = 19.17(4) d respectively 1.656288 × 106 seconds s.

Decay
mode
DaughterProbabilityDecay energyγ energy
(intensity)
EC/β+121Sb100 %1.056(26) MeV0.573139(11) MeV
80.4(22) %

 

Parent Nuclides

Direct parent isotope is: 121I.

 

Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear IsomerExcitation EnergyHalf-lifeSpin
121mTe293.974(22) keV164.2(8) d11/2-

 

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 69) and isobaric (same nucleon number A = 121) with Tellurium-121. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

 

ZIsotone N = 69Isobar A = 121
38107Sr
39108Y
40109Zr
41110Nb
42111Mo
43112Tc121Tc
44113Ru121Ru
45114Rh121Rh
46115Pd121Pd
47116Ag121Ag
48117Cd121Cd
49118In121In
50119Sn121Sn
51120Sb121Sb
52121Te121Te
53122I121I
54123Xe121Xe
55124Cs121Cs
56125Ba121Ba
57126La121La
58127Ce121Ce
59128Pr121Pr
60129Nd
61130Pm
62131Sm
63132Eu

 

External data and identifiers

CAS:14304-79-1InChI Key:PORWMNRCUJJQNO-NOHWODKXSA-NSMILES:[121Te]PubChem:ID 6337621Adopted Levels, Gammas:NuDat 121Te

 


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Last update: 2023-05-22


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