Atomic Number: 43
Atomic Weight: 98.9072
Discovery: Carlo Perrier, Emilio Segre 1937 (Italy) found it in a sample of molybdenum that had been bombarded with neutrons; erroneously reported Noddack, Tacke, Berg 1924 as Masurium.
Electron Configuration: [Kr] 5s2 4d5
Word Origin: Greek technikos: an art or technetos: artificial; this was the first element made artificially.
Isotopes: Twenty-one isotopes of technetium are known, with atomic masses ranging from 90-111. Technetium is one of two elements with Z < 83 with no stable isotopes; all of technetium's isotopes are radioactive. (The other element is promethium.) Some isotopes are produced as uranium fission products.
Properties: Technetium is a silvery-gray metal that tarnishes slowly in moist air. Common oxidation states are +7, +5, and +4. The chemistry of technetium is similar to that of rhenium. Technetium is a corrosion inhibitor for steel and is an excellent superconductor at 11K and below.
Uses: Technetium-99 is used in many medical radioactive isotope tests. Mild carbon steels may be effectively protected by minute quantities of technetium, but this corrosion protection is limited to closed systems because of technetium's radioactivity.
Element Classification: Transition Metal
Density (g/cc): 11.5
Melting Point (K): 2445
Boiling Point (K): 5150
Appearance: silvery-gray metal
Atomic Radius (pm): 136
Covalent Radius (pm): 127
Ionic Radius: 56 (+7e)
Atomic Volume (cc/mol): 8.5
Specific Heat (@20°C J/g mol): 0.243
Fusion Heat (kJ/mol): 23.8
Evaporation Heat (kJ/mol): 585
Pauling Negativity Number: 1.9
First Ionizing Energy (kJ/mol): 702.2
Oxidation States: 7
Lattice Structure: Hexagonal
Lattice Constant (Å): 2.740
Lattice C/A Ratio: 1.604
References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange's Handbook of Chemistry (1952), CRC Handbook of Chemistry & Physics (18th Ed.)
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