Xenon-128

Properties and data of the isotope ¹²⁸Xe.

Content

General data

Name of the isotope:Xenon-128; Xe-128Symbol:¹²⁸Xe or 12854XeMass number A:128 (= number of nucleons)Atomic number Z:54 (= number of protons)Neutrons N:74Isotopic mass:127.903531(7) u (atomic weight of Xenon-128)Nuclide mass:127.8739096 u (calculated nuclear mass without electrons)Mass excess:-89.86029 MeVMass defect:1.160224512 u (per nucleus)Nuclear binding energy:1080.74217158 MeV (per nucleus)
8.44329822 MeV (average binding energy per nucleon)Separation energy:S_N = 9.610(4) MeV (first neutron)
S_P = 8.165(4) MeV (first proton)Half-life:stableSpin and parity:
(nuclear angular momentum)0+Charge radius:4.7774(50) femtometer fmYear of discovery:1922

Parent Nuclides

Direct parent isotopes are: ¹²⁸Cs, ¹²⁸I.

Occurrence

Comparison of the natural Xenon isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):

	Atomic Mass m_a	Quantity	Half-life	Spin
Xenon Isotopic mixture	131.293 u	100 %
Isotope ¹²⁴Xe	123.90589(2) u	0.095(5) %	> 1.8 × 10²² a	0+
Isotope ¹²⁶Xe	125.90430(3) u	0.089(3) %	stable	0+
Isotope ¹²⁸Xe	127.903531(7) u	1.910(13) %	stable	0+
Isotope ¹²⁹Xe	128.90478086(4) u	26.401(138) %	stable	1/2+
Isotope ¹³⁰Xe	129.9035094(1) u	4.071(22) %	stable	0+
Isotope ¹³¹Xe	130.905084(2) u	21.232(51) %	stable	3/2+
Isotope ¹³²Xe	131.90415509(4) u	26.909(55) %	stable	0+
Isotope ¹³⁴Xe	133.905393033(10) u	10.436(35) %	5.8 × 10²² a	0+
Isotope ¹³⁶Xe	135.90721448(7) u	8.857(72) %	2.165(61) × 10²¹ a	0+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 74) and isobaric (same nucleon number A = 128) with Xenon-128. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 74	Isobar A = 128
41	¹¹⁵Nb
42	¹¹⁶Mo
43	¹¹⁷Tc
44	¹¹⁸Ru
45	¹¹⁹Rh
46	¹²⁰Pd	¹²⁸Pd
47	¹²¹Ag	¹²⁸Ag
48	¹²²Cd	¹²⁸Cd
49	¹²³In	¹²⁸In
50	¹²⁴Sn	¹²⁸Sn
51	¹²⁵Sb	¹²⁸Sb
52	¹²⁶Te	¹²⁸Te
53	¹²⁷I	¹²⁸I
54	¹²⁸Xe	¹²⁸Xe
55	¹²⁹Cs	¹²⁸Cs
56	¹³⁰Ba	¹²⁸Ba
57	¹³¹La	¹²⁸La
58	¹³²Ce	¹²⁸Ce
59	¹³³Pr	¹²⁸Pr
60	¹³⁴Nd	¹²⁸Nd
61	¹³⁵Pm	¹²⁸Pm
62	¹³⁶Sm	¹²⁸Sm
63	¹³⁷Eu
64	¹³⁸Gd
65	¹³⁹Tb
66	¹⁴⁰Dy
67	¹⁴¹Ho