Tantalum-156

Properties and data of the isotope ¹⁵⁶Ta.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Tantalum-156 is a radioisotope of the chemical element tantalum, which has 83 neutrons in its atomic nucleus in addition to the element-specific 73 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 156. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ¹⁵⁶Ta is exclusively for academic purposes.

General data

Name of the isotope:Tantalum-156; Ta-156Symbol:¹⁵⁶Ta or 15673TaMass number A:156 (= number of nucleons)Atomic number Z:73 (= number of protons)Neutrons N:83Isotopic mass:155.97209(32) u (atomic weight of Tantalum-156)Nuclide mass:155.9320476 u (calculated nuclear mass without electrons)Mass excess:14528561287.182 MeVMass defect:-15597051.709585 u (per nucleus)Nuclear binding energy:-14528560085.168 MeV (per nucleus)
-93131795.417743 MeV (average binding energy per nucleon)Separation energy:S_N = 10.084(424) MeV (first neutron)Half-life:333 msDecay constant λ:2.0815230647446 s^-1Specific activity α:8.036838577401 × 10⁺¹⁶ Bq g^-1
2172118.5344328 Ci g^-1Spin and parity:
(nuclear angular momentum)(2-)Year of discovery:1992

Radioactive Decay

Tantalum is a decay product of, among others, tungsten-156; during the production of this isotope, the half-life of ¹⁵⁶Ta was re-measured as t_1/2 = 333+25-22 ms [2] and adopted here; the previous official value is 106(4) ms.

Half-life T_½ = 333 ms respectively 3.33 × 10^-1 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	¹⁵⁶Hf	29(3) %	11.96(33) MeV
p	¹⁵⁵Hf	71(3) %

Parent Nuclides

Direct parent isotopes are: ¹⁶⁰Re, ¹⁵⁶W.

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
^156mTa	102(7) keV	0.36(4) s	9+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 83) and isobaric (same nucleon number A = 156) with Tantalum-156. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 83	Isobar A = 156
46	¹²⁹Pd
47	¹³⁰Ag
48	¹³¹Cd
49	¹³²In
50	¹³³Sn
51	¹³⁴Sb
52	¹³⁵Te
53	¹³⁶I
54	¹³⁷Xe
55	¹³⁸Cs
56	¹³⁹Ba
57	¹⁴⁰La	¹⁵⁶La
58	¹⁴¹Ce	¹⁵⁶Ce
59	¹⁴²Pr	¹⁵⁶Pr
60	¹⁴³Nd	¹⁵⁶Nd
61	¹⁴⁴Pm	¹⁵⁶Pm
62	¹⁴⁵Sm	¹⁵⁶Sm
63	¹⁴⁶Eu	¹⁵⁶Eu
64	¹⁴⁷Gd	¹⁵⁶Gd
65	¹⁴⁸Tb	¹⁵⁶Tb
66	¹⁴⁹Dy	¹⁵⁶Dy
67	¹⁵⁰Ho	¹⁵⁶Ho
68	¹⁵¹Er	¹⁵⁶Er
69	¹⁵²Tm	¹⁵⁶Tm
70	¹⁵³Yb	¹⁵⁶Yb
71	¹⁵⁴Lu	¹⁵⁶Lu
72	¹⁵⁵Hf	¹⁵⁶Hf
73	¹⁵⁶Ta	¹⁵⁶Ta
74	¹⁵⁷W	¹⁵⁶W