Iodine-129

Properties and data of the isotope ¹²⁹I.

Content

General data

Name of the isotope:Iodine-129; I-129Other names:Jod-129Symbol:¹²⁹I or 12953IMass number A:129 (= number of nucleons)Atomic number Z:53 (= number of protons)Neutrons N:76Isotopic mass:128.904984(3) u (atomic weight of Iodine-129)Nuclide mass:128.8759111 u (calculated nuclear mass without electrons)Mass excess:-88.50683 MeVMass defect:1.168276312 u (per nucleus)Nuclear binding energy:1088.24237497 MeV (per nucleus)
8.4359874 MeV (average binding energy per nucleon)Separation energy:S_N = 8.840(5) MeV (first neutron)
S_P = 6.802(3) MeV (first proton)Half-life:1.57(4) × 10⁷ aDecay constant λ:1.399971522910 × 10^-15 s^-1Specific activity α:6586582.5866132 Bq g^-1
0.00017801574558414 Ci g^-1Spin and parity:
(nuclear angular momentum)7/2+Magnetic dipole moment:μ(μ_N) = +2.6165(14)Quadrupole moment Q:- 0.488(8) barn (100 fm²)Nuclear g-factor:g_l = 0.74757142857143Year of discovery:1951

Radioactive Decay

Half-life T_½ = 1.57(4) × 10⁷ a respectively 4.951152 × 10¹⁴ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	¹²⁹Xe	100 %	0.189(3) MeV

Parent Nuclides

Direct parent isotope is: ¹²⁹Te.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 76) and isobaric (same nucleon number A = 129) with Iodine-129. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 76	Isobar A = 129
42	¹¹⁸Mo
43	¹¹⁹Tc
44	¹²⁰Ru
45	¹²¹Rh
46	¹²²Pd	¹²⁹Pd
47	¹²³Ag	¹²⁹Ag
48	¹²⁴Cd	¹²⁹Cd
49	¹²⁵In	¹²⁹In
50	¹²⁶Sn	¹²⁹Sn
51	¹²⁷Sb	¹²⁹Sb
52	¹²⁸Te	¹²⁹Te
53	¹²⁹I	¹²⁹I
54	¹³⁰Xe	¹²⁹Xe
55	¹³¹Cs	¹²⁹Cs
56	¹³²Ba	¹²⁹Ba
57	¹³³La	¹²⁹La
58	¹³⁴Ce	¹²⁹Ce
59	¹³⁵Pr	¹²⁹Pr
60	¹³⁶Nd	¹²⁹Nd
61	¹³⁷Pm	¹²⁹Pm
62	¹³⁸Sm	¹²⁹Sm
63	¹³⁹Eu
64	¹⁴⁰Gd
65	¹⁴¹Tb
66	¹⁴²Dy
67	¹⁴³Ho
68	¹⁴⁴Er
69	¹⁴⁵Tm