Technetium

Technetium, ₄₃Tc

Technetium
Pronunciation	/tɛkˈniːʃ(i)əm/ ​(tek-NEE-sh(ee-)əm)
Appearance	shiny gray metal
Mass number	[97]
Technetium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Mn ↑ Tc ↓ Re molybdenum ← technetium → ruthenium
Atomic number (Z)	43
Group	group 7
Period	period 5
Block	d-block
Electron configuration	[Kr] 4d5 5s2
Electrons per shell	2, 8, 18, 13, 2
Physical properties
Phase at STP	solid
Melting point	2430 K ​(2157 °C, ​3915 °F)
Boiling point	4538 K ​(4265 °C, ​7709 °F)
Density (at 20° C)	98Tc: 11.359 g/cm3 99Tc: 11.475 g/cm3[1]
Heat of fusion	33.29 kJ/mol
Heat of vaporization	585.2 kJ/mol
Molar heat capacity	24.27 J/(mol·K)
Vapor pressure (extrapolated) P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 2727 2998 3324 3726 4234 4894
Atomic properties
Oxidation states	−1, 0, +1,[2][citation needed] +2, +3, +4, +5, +6, +7 (a strongly acidic oxide)
Electronegativity	Pauling scale: 1.9
Ionization energies	1st: 686.9[3] kJ/mol 2nd: 1470 kJ/mol 3rd: 2850 kJ/mol
Atomic radius	empirical: 136 pm
Covalent radius	147±7 pm
Van der Waals radius	205 pm
Spectral lines of technetium
Other properties
Natural occurrence	from decay
Crystal structure	​hexagonal close-packed (hcp) (hP2)
Lattice constants	a = 274.12 pm c = 439.90 pm (at 20 °C)[1]
Thermal expansion	8.175×10−6/K (at 20 °C)[1]
Thermal conductivity	50.6 W/(m⋅K)
Electrical resistivity	200 nΩ⋅m (at 20 °C)
Magnetic ordering	Paramagnetic
Molar magnetic susceptibility	+270.0×10−6 cm3/mol (298 K)[4]
Speed of sound thin rod	16,200 m/s (at 20 °C)
CAS Number	7440-26-8
History
Prediction	Dmitri Mendeleev (1871)
Discovery and first isolation	Emilio Segrè and Carlo Perrier (1937)
Isotopes of technetium v e
Main isotopes[5] Decay abun­dance half-life (t1/2) mode pro­duct 95mTc synth 61.96 d β+ 95Mo IT 95Tc Preview warning: Unknown parameter cat:#U "perdc1" 96Tc synth 4.28 d β+ 96Mo γ – 97Tc synth 4.21×106 y ε 97Mo 97mTc synth 91.1 d IT 97Tc ε ... Preview warning: Infobox Tc isotopes: Decay product missing; pn2, ps2 for "dm2=epsi_link" cat#P 98Tc synth 4.2×106 y β− 98Ru β+ – 99Tc trace 2.111×105 y β− 99Ru 99mTc synth 6.01 h IT 99Tc β− –
Category: Technetium view talk edit | references

Technetium is a chemical element; it has symbol Tc and atomic number 43. It is the lightest element whose isotopes are all radioactive. Technetium and promethium are the only radioactive elements whose neighbours in the sense of atomic number are both stable. All available technetium is produced as a synthetic element. Naturally occurring technetium is a spontaneous fission product in uranium ore and thorium ore (the most common source), or the product of neutron capture in molybdenum ores. This silvery gray, crystalline transition metal lies between manganese and rhenium in group 7 of the periodic table, and its chemical properties are intermediate between those of both adjacent elements. The most common naturally occurring isotope is ⁹⁹Tc, in traces only.

Many of technetium's properties had been predicted by Dmitri Mendeleev before it was discovered. Mendeleev noted a gap in his periodic table and gave the undiscovered element the provisional name ekamanganese (Em). In 1937, technetium became the first predominantly artificial element to be produced, hence its name (from the Greek τεχνητός, technetos, from techne, as in "craft", "art" and having the meaning of "artificial", + -ium).

One short-lived gamma ray-emitting nuclear isomer, technetium-99m, is used in nuclear medicine for a wide variety of tests, such as bone cancer diagnoses. The ground state of the nuclide technetium-99 is used as a gamma-ray-free source of beta particles. Long-lived technetium isotopes produced commercially are byproducts of the fission of uranium-235 in nuclear reactors and are extracted from nuclear fuel rods. Because even the longest-lived isotope of technetium has a relatively short half-life (4.21 million years), the 1952 detection of technetium in red giants helped to prove that stars can produce heavier elements.