2
1 Introduction General Information on Technetium
vacant places in the periodic table. A chemical analysis revealed that the columbite
sample contained about 0.5 wt% of the newly discovered rhenium. The presence
of the sought-after eka-manganese was deduced from the recorded X-ray lines: K1:
0.672 Å, K2: 0.675 Å and K1: 0.601 Å. Using a relation between X-ray frequencies
of atoms and their atomic number presented by Moseley (1914), they identified
lines of elements 43 and 75. However, other authors were unable to obtain the same
results when repeating the measurements reported by Noddack et al. and the reported
discovery of the technetium by the latter authors could not be confirmed. Therefore,
the discussion about history of the discovery of the technetium could not be settled
even until today (see: Armstrong 2003; Zingales 2006).
Today, Carlo Perrier and Emilio Segrè are credited with the discovery of the
element with atomic number of 43. In 1937, they announced the discovery of radioactive isotopes of the new element in a sample prepared by the E. O. Lawrence (Perrier
and Segrè 1937). The sample was a molybdenum plate subjected to several months
of bombardment with deuterium nuclei (and secondary neutrons) in the University
of California cyclotron in 1936. The cyclotron experiments were completed by the
end of December 1936, and the irradiated plate was sent to Perrier at the University
of Palermo in Italy, where in 1937 Perrier and Segrè detected strong ionizing radiation identified as slow electrons. In the first published study, Cacciapuoti and Segrè
(1937) reported three radioactive species present in the analyzed plate, with only one
of them being active enough to determine its half-life precisely. Today we know that
this was
97m Tc. In the next publication, Cacciapuoti (1939) reported
95m Tc as the
second discovered radioisotope of the Element 43.
Shortly after the discovery of the new element, the name panorama was proposed,
after Panormus, a Latin name for Palermo, but this was not accepted. The new element
is named technetium after the Greek word technètos, which means “artificial.” The
name was officially accepted by the 15th Conference of Pure and Applied Chemistry
in 1949.
Measurable amounts of technetium were obtained for the first time in 1946 in
the Oak Ridge reactor (USA) after neutron irradiation of a plate containing 4 kg of
molybdenum. After completing the irradiation, the plate was subjected to a chemical treatment and, subsequently, 0.1 mg of metallic technetium were galvanically
deposited on a copper foil (see: Enghag 2004).
Technetium is generated in stellar nucleosynthesis and its presence in the atmosphere of stars has been confirmed by means of analysis of stellar spectra (Merrill
1952). The TcI spectral lines are particularly intense for s-type stars. The technetium
nucleosynthesis takes place in the star interior and the so formed Tc nuclei/atoms
are transported toward the star surface. When the rate of the transport process is
faster than or comparable to the decay rate of the longest living technetium isotope,
i.e.,
99 Tc, the latter nuclei may reach the star surface before they completely decay
(Burbidge et al. 1957). This explains why Tc lines are present in the stellar spectra.
The
99 Tc of stellar origin was most likely present in primordial material from which
the Earth was formed. The half-life of this isotope (2.11 · 10
5 y) is relatively short
1 Introduction General Information on Technetium
vacant places in the periodic table. A chemical analysis revealed that the columbite
sample contained about 0.5 wt% of the newly discovered rhenium. The presence
of the sought-after eka-manganese was deduced from the recorded X-ray lines: K1:
0.672 Å, K2: 0.675 Å and K1: 0.601 Å. Using a relation between X-ray frequencies
of atoms and their atomic number presented by Moseley (1914), they identified
lines of elements 43 and 75. However, other authors were unable to obtain the same
results when repeating the measurements reported by Noddack et al. and the reported
discovery of the technetium by the latter authors could not be confirmed. Therefore,
the discussion about history of the discovery of the technetium could not be settled
even until today (see: Armstrong 2003; Zingales 2006).
Today, Carlo Perrier and Emilio Segrè are credited with the discovery of the
element with atomic number of 43. In 1937, they announced the discovery of radioactive isotopes of the new element in a sample prepared by the E. O. Lawrence (Perrier
and Segrè 1937). The sample was a molybdenum plate subjected to several months
of bombardment with deuterium nuclei (and secondary neutrons) in the University
of California cyclotron in 1936. The cyclotron experiments were completed by the
end of December 1936, and the irradiated plate was sent to Perrier at the University
of Palermo in Italy, where in 1937 Perrier and Segrè detected strong ionizing radiation identified as slow electrons. In the first published study, Cacciapuoti and Segrè
(1937) reported three radioactive species present in the analyzed plate, with only one
of them being active enough to determine its half-life precisely. Today we know that
this was
97m Tc. In the next publication, Cacciapuoti (1939) reported
95m Tc as the
second discovered radioisotope of the Element 43.
Shortly after the discovery of the new element, the name panorama was proposed,
after Panormus, a Latin name for Palermo, but this was not accepted. The new element
is named technetium after the Greek word technètos, which means “artificial.” The
name was officially accepted by the 15th Conference of Pure and Applied Chemistry
in 1949.
Measurable amounts of technetium were obtained for the first time in 1946 in
the Oak Ridge reactor (USA) after neutron irradiation of a plate containing 4 kg of
molybdenum. After completing the irradiation, the plate was subjected to a chemical treatment and, subsequently, 0.1 mg of metallic technetium were galvanically
deposited on a copper foil (see: Enghag 2004).
Technetium is generated in stellar nucleosynthesis and its presence in the atmosphere of stars has been confirmed by means of analysis of stellar spectra (Merrill
1952). The TcI spectral lines are particularly intense for s-type stars. The technetium
nucleosynthesis takes place in the star interior and the so formed Tc nuclei/atoms
are transported toward the star surface. When the rate of the transport process is
faster than or comparable to the decay rate of the longest living technetium isotope,
i.e.,
99 Tc, the latter nuclei may reach the star surface before they completely decay
(Burbidge et al. 1957). This explains why Tc lines are present in the stellar spectra.
The
99 Tc of stellar origin was most likely present in primordial material from which
the Earth was formed. The half-life of this isotope (2.11 · 10
5 y) is relatively short