Uranium-218m

Properties and data of the isotope ^218mU.

Contents

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

General data

Name of the isotope:Uranium-218m; U-218mSymbol:^218mU or 218m92UMass number A:218 (= number of nucleons)Atomic number Z:92 (= number of protons)Neutrons N:126Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.3695652173913 (= neutron-proton ratio)Neutron excess (N-Z):34Excitation energy:2105(19) keVIsotopic mass:218.023505(15) u (atomic weight of Uranium-218m)Nuclide mass:217.9730423 u (calculated nuclear mass without electrons)Mass excess:21.89477 MeVMass defect:1.78817736 u (per nucleus)Nuclear binding energy:1665.67648178 MeV (per nucleus)
7.64071781 MeV (average binding energy per nucleon)Half-life:0.56 msDecay constant λ:1237.7628224285 s^-1Specific activity α:3.419257829292 × 10⁺²⁴ Bq g^-1
92412373764657 Ci g^-1Spin and parity:
(nuclear angular momentum)(8+)

Radioactive Decay

Half-life T_½ = 0.56 ms respectively 5.6 × 10^-4 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²¹⁴Th	100 %

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
²¹⁸U		0.51 ms	0+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 126) and isobaric (same nucleon number A = 218) with Uranium-218m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 126	Isobar A = 218
76	²⁰²Os
77	²⁰³Ir
78	²⁰⁴Pt
79	²⁰⁵Au
80	²⁰⁶Hg
81	²⁰⁷Tl
82	²⁰⁸Pb	²¹⁸Pb
83	²⁰⁹Bi	²¹⁸Bi
84	²¹⁰Po	²¹⁸Po
85	²¹¹At	²¹⁸At
86	²¹²Rn	²¹⁸Rn
87	²¹³Fr	²¹⁸Fr
88	²¹⁴Ra	²¹⁸Ra
89	²¹⁵Ac	²¹⁸Ac
90	²¹⁶Th	²¹⁸Th
91	²¹⁷Pa	²¹⁸Pa
92	²¹⁸U	²¹⁸U
93	²¹⁹Np