Cesium-117

Properties and data of the isotope ¹¹⁷Cs.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

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

General data

Name of the isotope:Cesium-117; Cs-117Symbol:¹¹⁷Cs or 11755CsMass number A:117 (= number of nucleons)Atomic number Z:55 (= number of protons)Neutrons N:62Excitation energy:+yIsotopic mass:116.92862(7) u (atomic weight of Cesium-117)Nuclide mass:116.8984501 u (calculated nuclear mass without electrons)Mass excess:-66.49004 MeVMass defect:1.038981552 u (per nucleus)Nuclear binding energy:967.8050818 MeV (per nucleus)
8.27183831 MeV (average binding energy per nucleon)Separation energy:S_N = 12.52(12) MeV (first neutron)
S_P = 0.74(6) MeV (first proton)Half-life:8.4(6) sDecay constant λ:0.082517521495232 s^-1Specific activity α:4.283897740147 × 10⁺²⁰ Bq g^-1
11578102000.399 Ci g^-1Spin and parity:
(nuclear angular momentum)(9/2+)Year of discovery:1972

Radioactive Decay

Half-life T_½ = 8.4(6) s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	¹¹⁷Xe	100 %	7.69(6) MeV

Parent Nuclides

Direct parent isotope is: ¹¹⁷Ba.

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
^117mCs	+z keV	6.5(4) s	(3/2+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 62) and isobaric (same nucleon number A = 117) with Cesium-117. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 62	Isobar A = 117
35	⁹⁷Br
36	⁹⁸Kr
37	⁹⁹Rb
38	¹⁰⁰Sr
39	¹⁰¹Y
40	¹⁰²Zr
41	¹⁰³Nb
42	¹⁰⁴Mo	¹¹⁷Mo
43	¹⁰⁵Tc	¹¹⁷Tc
44	¹⁰⁶Ru	¹¹⁷Ru
45	¹⁰⁷Rh	¹¹⁷Rh
46	¹⁰⁸Pd	¹¹⁷Pd
47	¹⁰⁹Ag	¹¹⁷Ag
48	¹¹⁰Cd	¹¹⁷Cd
49	¹¹¹In	¹¹⁷In
50	¹¹²Sn	¹¹⁷Sn
51	¹¹³Sb	¹¹⁷Sb
52	¹¹⁴Te	¹¹⁷Te
53	¹¹⁵I	¹¹⁷I
54	¹¹⁶Xe	¹¹⁷Xe
55	¹¹⁷Cs	¹¹⁷Cs
56	¹¹⁸Ba	¹¹⁷Ba
57	¹¹⁹La	¹¹⁷La
58	¹²⁰Ce
59	¹²¹Pr