Cesium-125

Properties and data of the isotope ¹²⁵Cs.

Content

General data

Name of the isotope:Cesium-125; Cs-125Symbol:¹²⁵Cs or 12555CsMass number A:125 (= number of nucleons)Atomic number Z:55 (= number of protons)Neutrons N:70Isotopic mass:124.909728(8) u (atomic weight of Cesium-125)Nuclide mass:124.8795581 u (calculated nuclear mass without electrons)Mass excess:-84.08783 MeVMass defect:1.12719288 u (per nucleus)Nuclear binding energy:1049.97340456 MeV (per nucleus)
8.39978724 MeV (average binding energy per nucleon)Separation energy:S_N = 10.428(11) MeV (first neutron)
S_P = 3.715(8) MeV (first proton)Half-life:46.7(1) minDecay constant λ:0.00024737586743753 s^-1Specific activity α:1.201397031498 × 10⁺¹⁸ Bq g^-1
32470190.040492 Ci g^-1Spin and parity:
(nuclear angular momentum)1/2(+)Magnetic dipole moment:μ(μ_N) = + 1.407(7)Nuclear g-factor:g_l = 2.814Charge radius:4.7880(62) femtometer fmYear of discovery:1954

Radioactive Decay

Half-life T_½ = 46.7(1) min (minutes) respectively 2.802 × 10³ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EE/β⁺	¹²⁵Xe	100 %	3.105(8) MeV

Parent Nuclides

Direct parent isotope is: ¹²⁵Ba.

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
^125mCs	266.1(11) keV	0.90(3) ms	(11/2-)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 70) and isobaric (same nucleon number A = 125) with Cesium-125. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 70	Isobar A = 125
39	¹⁰⁹Y
40	¹¹⁰Zr
41	¹¹¹Nb
42	¹¹²Mo
43	¹¹³Tc
44	¹¹⁴Ru
45	¹¹⁵Rh	¹²⁵Rh
46	¹¹⁶Pd	¹²⁵Pd
47	¹¹⁷Ag	¹²⁵Ag
48	¹¹⁸Cd	¹²⁵Cd
49	¹¹⁹In	¹²⁵In
50	¹²⁰Sn	¹²⁵Sn
51	¹²¹Sb	¹²⁵Sb
52	¹²²Te	¹²⁵Te
53	¹²³I	¹²⁵I
54	¹²⁴Xe	¹²⁵Xe
55	¹²⁵Cs	¹²⁵Cs
56	¹²⁶Ba	¹²⁵Ba
57	¹²⁷La	¹²⁵La
58	¹²⁸Ce	¹²⁵Ce
59	¹²⁹Pr	¹²⁵Pr
60	¹³⁰Nd	¹²⁵Nd
61	¹³¹Pm
62	¹³²Sm
63	¹³³Eu
64	¹³⁴Gd
65	¹³⁵Tb