Iodine-121

Properties and data of the isotope ¹²¹I.

Content

General data

Name of the isotope:Iodine-121; I-121Other names:Jod-121Symbol:¹²¹I or 12153IMass number A:121 (= number of nucleons)Atomic number Z:53 (= number of protons)Neutrons N:68Isotopic mass:120.907405(6) u (atomic weight of Iodine-121)Nuclide mass:120.8783321 u (calculated nuclear mass without electrons)Mass excess:-86.25169 MeVMass defect:1.096535984 u (per nucleus)Nuclear binding energy:1021.41668988 MeV (per nucleus)
8.44146025 MeV (average binding energy per nucleon)Separation energy:S_N = 10.570(16) MeV (first neutron)
S_P = 4.172(4) MeV (first proton)Half-life:2.12(1) hDecay constant λ:9.082117145701 × 10^-5 s^-1Specific activity α:4.557815729821 × 10⁺¹⁷ Bq g^-1
12318420.89141 Ci g^-1Spin and parity:
(nuclear angular momentum)5/2+Magnetic dipole moment:μ(μ_N) = 2.3(1)Nuclear g-factor:g_l = 0.92Year of discovery:1950

Radioactive Decay

Half-life T_½ = 2.12(1) h (hours) respectively 7.632 × 10³ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE/β⁺	¹²¹Te	100 %	2.294(26) MeV

Parent Nuclides

Direct parent isotope is: ¹²¹Xe.

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
^121mI	2376.9(4) keV	9.0(14) μs

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 68) and isobaric (same nucleon number A = 121) with Iodine-121. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 68	Isobar A = 121
38	¹⁰⁶Sr
39	¹⁰⁷Y
40	¹⁰⁸Zr
41	¹⁰⁹Nb
42	¹¹⁰Mo
43	¹¹¹Tc	¹²¹Tc
44	¹¹²Ru	¹²¹Ru
45	¹¹³Rh	¹²¹Rh
46	¹¹⁴Pd	¹²¹Pd
47	¹¹⁵Ag	¹²¹Ag
48	¹¹⁶Cd	¹²¹Cd
49	¹¹⁷In	¹²¹In
50	¹¹⁸Sn	¹²¹Sn
51	¹¹⁹Sb	¹²¹Sb
52	¹²⁰Te	¹²¹Te
53	¹²¹I	¹²¹I
54	¹²²Xe	¹²¹Xe
55	¹²³Cs	¹²¹Cs
56	¹²⁴Ba	¹²¹Ba
57	¹²⁵La	¹²¹La
58	¹²⁶Ce	¹²¹Ce
59	¹²⁷Pr	¹²¹Pr
60	¹²⁸Nd
61	¹²⁹Pm
62	¹³⁰Sm
63	¹³¹Eu