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 (near r.t.)	11 g/cm3
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	−3, −1, 0, +1, +2, +3, +4, +5, +6, +7 (a strongly acidic oxide)
Electronegativity	Pauling scale: 1.9
Ionization energies	1st: 702 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)
Speed of sound thin rod	16,200 m/s (at 20 °C)
Thermal expansion	7.1 µm/(m⋅K) (at r.t.)
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)
CAS Number	7440-26-8
History
Prediction	Dmitri Mendeleev (1871)
Discovery and first isolation	Emilio Segrè and Carlo Perrier (1937)
Isotopes of technetium
Main isotopes Decay abun­dance half-life (t1/2) mode pro­duct 95mTc synth 61.96 d β+ 95Mo IT 95Tc 96Tc synth 4.28 d ε 96Mo γ – 97Tc synth 4.21×106 y ε 97Mo 97mTc synth 91.1 d IT 97Tc ε ... 98Tc synth 4.2×106 y β− 98Ru β+ – 99Tc trace 211.1×103 y β− 99Ru 99mTc synth 6.01 h IT 99Tc β− –

Technetium is a radioactive chemical element that has the chemical symbol Tc and has the atomic number 43. It is the lightest synthetic element.

Chemistry of Technetium

In the periodic table, it is placed in a group of metal elements named the transition metals. The color of technetium is silvery-grey and is a crystalline metal whose chemistry is similar to rhenium and manganese.

The isotope ^99mTc is used for many diagnostic test in nuclear medicine, even though it has a short half-life. ⁹⁹Tc is used as a source of beta particles without emitting gamma rays. The ion that has oxygen and technetium bonded together (TcO₄^-) is named the pertechnetate ion, which could be used as to prevent anodic corrosion in steel.

History

Before the element was found, many of the properties of element 43 were predicted by Dmitri Mendeleev. Mendeleev noticed a gap in his periodic table and named the element in the gap eka-manganese. In 1937 the technetium isotope ⁹⁷Tc was the first element to be artificially produced. This was the reason why he named it Technetium as in Greek, τεχνητος means "artificial". Most technetium made on Earth is a by-product of fission of uranium-235 in nuclear reactors and extracted from nuclear fuel rods. On earth, technetium occurs naturally only in uranium ores as a product of spontaneous fission. The amount of technetium in the ore is very small but has been measured. The longest half-life of Technetium is 4.2 million years (⁹⁸Tc). This means that its detection in red giants in 1952 helped support the theory that stars can produce heavier elements.