Iridium-204

Properties and data of the isotope ²⁰⁴Ir.

Contents

Iridium-204 is a radioisotope of the chemical element iridium, which has 127 neutrons in its atomic nucleus in addition to the element-specific 77 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 204. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ²⁰⁴Ir is exclusively for academic purposes.

Iridium-204 was first produced according to a 2011 publication as the product of a (p,n) charge exchange reaction induced by irradiation of beryllium-9 with a 1 A GeV lead-208beam [1]; the production cross-section was measured.

See also: List of individual Iridium isotopes (and general data sources).

General data

Name of the isotope:Iridium-204; Ir-204Symbol:²⁰⁴Ir or 20477IrMass number A:204 (= number of nucleons)Atomic number Z:77 (= number of protons)Neutrons N:127Nucleon pairing (Z - N):odd - oddNuclear ratio (N/Z ratio):1.6493506493506 (= neutron-proton ratio)Neutron excess (N-Z):50Isotopic mass:203.98973(43) u (atomic weight of Iridium-204)Nuclide mass:203.9474938 u (calculated nuclear mass without electrons)Mass excess:-9.56644 MeVMass defect:1.713241796 u (per nucleus)Nuclear binding energy:1595.87445352 MeV (per nucleus)
7.82291399 MeV (average binding energy per nucleon)Separation energy:S_N = 3.271(565) MeV (first neutron)
S_P = 9.589(565) MeV (first proton)Half-life:> 160 nsDecay constant λ:4332169.8784997 s^-1Specific activity α:1.285169322044 × 10⁺²⁸ Bq g^-1
3.473430600119 × 10⁺¹⁷ Ci g^-1Spin and parity:
(nuclear angular momentum)Year of discovery:2011

Radioactive Decay

Beta decay is theoretically expected for the nuclide iridium-204, but experimental proof is still pending.

Half-life T_½ = > 160 ns respectively 1.6 × 10^-7 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	²⁰⁴Pt	?	4.94(45) MeV
β^-, n	²⁰³Pt	?	1.87(45) MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 127) and isobaric (same nucleon number A = 204) with Iridium-204. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 127	Isobar A = 204
76	²⁰³Os
77	²⁰⁴Ir	²⁰⁴Ir
78	²⁰⁵Pt	²⁰⁴Pt
79	²⁰⁶Au	²⁰⁴Au
80	²⁰⁷Hg	²⁰⁴Hg
81	²⁰⁸Tl	²⁰⁴Tl
82	²⁰⁹Pb	²⁰⁴Pb
83	²¹⁰Bi	²⁰⁴Bi
84	²¹¹Po	²⁰⁴Po
85	²¹²At	²⁰⁴At
86	²¹³Rn	²⁰⁴Rn
87	²¹⁴Fr	²⁰⁴Fr
88	²¹⁵Ra	²⁰⁴Ra
89	²¹⁶Ac	²⁰⁴Ac
90	²¹⁷Th
91	²¹⁸Pa
92	²¹⁹U
93	²²⁰Np