Cesium-118

Properties and data of the isotope ¹¹⁸Cs.

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-118; Cs-118Symbol:¹¹⁸Cs or 11855CsMass number A:118 (= number of nucleons)Atomic number Z:55 (= number of protons)Neutrons N:63Nucleon pairing (Z - N):odd - oddNuclear ratio (N/Z ratio):1.1454545454545 (= neutron-proton ratio)Neutron excess (N-Z):8Isotopic mass:117.926560(14) u (atomic weight of Cesium-118)Nuclide mass:117.8963901 u (calculated nuclear mass without electrons)Mass excess:-68.40892 MeVMass defect:1.049706468 u (per nucleus)Nuclear binding energy:977.7952767 MeV (per nucleus)
8.28640065 MeV (average binding energy per nucleon)Separation energy:S_N = 9.99(6) MeV (first neutron)
S_P = 1.513(16) MeV (first proton)Half-life:14(2) sDecay constant λ:0.049510512897139 s^-1Specific activity α:2.548369937728 × 10⁺²⁰ Bq g^-1
6887486318.1862 Ci g^-1Spin and parity:
(nuclear angular momentum)2Magnetic dipole moment:μ(μ_N) = + 3.870(5)Quadrupole moment Q:+ 0.14(2) barn (100 fm²)Nuclear g-factor:g_l = 1.935Charge radius:4.7832(92) femtometer fmYear of discovery:1969

Radioactive Decay

Half-life T_½ = 14(2) s respectively 1.4 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy
EC/β⁺	¹¹⁸Xe	99.95 %	9.670(16) MeV
EC, p	¹¹⁷I	0.042 %
EC, α	¹¹⁴Te	0.0024 %

Parent Nuclides

Direct parent isotope is: ¹¹⁸Ba.

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
^118mCs	180 keV	17(3) s	(6,7,8)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 63) and isobaric (same nucleon number A = 118) with Cesium-118. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 63	Isobar A = 118
35	⁹⁸Br
36	⁹⁹Kr
37	¹⁰⁰Rb
38	¹⁰¹Sr
39	¹⁰²Y
40	¹⁰³Zr
41	¹⁰⁴Nb
42	¹⁰⁵Mo	¹¹⁸Mo
43	¹⁰⁶Tc	¹¹⁸Tc
44	¹⁰⁷Ru	¹¹⁸Ru
45	¹⁰⁸Rh	¹¹⁸Rh
46	¹⁰⁹Pd	¹¹⁸Pd
47	¹¹⁰Ag	¹¹⁸Ag
48	¹¹¹Cd	¹¹⁸Cd
49	¹¹²In	¹¹⁸In
50	¹¹³Sn	¹¹⁸Sn
51	¹¹⁴Sb	¹¹⁸Sb
52	¹¹⁵Te	¹¹⁸Te
53	¹¹⁶I	¹¹⁸I
54	¹¹⁷Xe	¹¹⁸Xe
55	¹¹⁸Cs	¹¹⁸Cs
56	¹¹⁹Ba	¹¹⁸Ba
57	¹²⁰La	¹¹⁸La
58	¹²¹Ce
59	¹²²Pr