See also: List of individual Technetium isotopes (and general data sources).
General data
Name of the isotope:Technetium-99m; Tc-99mSymbol:99mTc or 99m43TcMass number A:99 (= number of nucleons)Atomic number Z:43 (= number of protons)Neutrons N:56Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):1.3023255813953 (= neutron-proton ratio)Neutron excess (N-Z):13Excitation energy:142.6836(11) keVIsotopic mass:98.9062497(10) u (atomic weight of Technetium-99m)Nuclide mass:98.8826619 u (calculated nuclear mass without electrons)Mass excess:-87.32784 MeVMass defect:0.915461972 u (per nucleus)Nuclear binding energy:852.74733415 MeV (per nucleus) 8.61360944 MeV (average binding energy per nucleon)Half-life:6.0066(2) h (NUBASE2020)Decay constant λ:3.205168522587 × 10-5 s-1Specific activity α:1.951542603332 × 10+17 Bq g-1 5274439.4684673 Ci g-1Spin and parity: (nuclear angular momentum)1/2-Year of discovery:1938
Radioactive Decay
Half-life T½ = 6.0066(2) h (hours) respectively 2.162592 × 104 seconds s.
Decay mode
Daughter
Probability
Decay energy
γ energy (intensity)
β-
99Ru
0.0037(6) %
0.4401836(11) MeV
0.0896(3) MeV 0.00104(19) %
Iso
99Tc
99.9963(6) %
0.1426836(11) MeV
0.140511(1) MeV 89(4) %
Occurrence
Comparison of the natural Technetium isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):
Atomic Mass ma
Quantity
Half-life
Spin
Technetium Isotopic mixture
98.9062547 u
100 %
Isotope 99Tc
98.9062497(10) u
6.0066(2) h
1/2-
Nuclear Isomers
Nuclear isomers or excited states with the activation energy in keV related to the ground state.
The following table shows the atomic nuclei that are isotonic (same neutron number N = 56) and isobaric (same nucleon number A = 99) with Technetium-99m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
