See also: List of individual Cesium isotopes (and general data sources).
General data
Name of the isotope:Cesium-128; Cs-128Symbol:128Cs or 12855CsMass number A:128 (= number of nucleons)Atomic number Z:55 (= number of protons)Neutrons N:73Nucleon pairing (Z - N):odd - oddNuclear ratio (N/Z ratio):1.3272727272727 (= neutron-proton ratio)Neutron excess (N-Z):18Isotopic mass:127.907749(6) u (atomic weight of Cesium-128)Nuclide mass:127.8775791 u (calculated nuclear mass without electrons)Mass excess:-85.93125 MeVMass defect:1.155166628 u (per nucleus)Nuclear binding energy:1076.03078298 MeV (per nucleus) 8.40649049 MeV (average binding energy per nucleon)Separation energy:SN = 7.763(8) MeV (first neutron) SP = 4.899(7) MeV (first proton)Half-life:3.640(14) minDecay constant λ:0.0031737508267397 s-1Specific activity α:1.494262416876 × 10+19 Bq g-1 403854707.26381 Ci g-1Spin and parity: (nuclear angular momentum)1+Magnetic dipole moment:μ(μN) = + 0.972(5)Quadrupole moment Q:- 0.570(8) barn (100 fm2)Nuclear g-factor:gl = 0.972Charge radius:4.7921(52) femtometer fmYear of discovery:1951
Radioactive Decay
Half-life T½ = 3.640(14) min (minutes) respectively 2.184 × 102 seconds s.
The following table shows the atomic nuclei that are isotonic (same neutron number N = 73) and isobaric (same nucleon number A = 128) with Cesium-128. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
