Hafnium

Hafnium, ₇₂Hf

Hafnium
Pronunciation	/ˈhæfniəm/ ​(HAF-nee-əm)
Appearance	steel gray
Standard atomic weight Ar, std(Hf)	7002178490000000000♠178.49(2)
Mass number	Hf:
Hafnium in the periodic cairt
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 Airn Cobalt Nickel Capper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Siller (element) 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 Gowd Mercur (element) Thallium Leid (element) 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 Ununtrium Flerovium Ununpentium Livermorium Ununseptium Ununoctium Zr ↑ Hf ↓ Rf lutetium ← hafnium → tantalum
Atomic nummer (Z)	72
Group	group 4
Period	period 6
Block	d-block
Element category	Transeetion metal
Electron confeeguration	[Xe] 4f14 5d2 6s2
Electrons per shell	2, 8, 18, 32, 10, 2
Pheesical properties
Phase at STP	solit
Meltin pynt	2506 K ​(2233 °C, ​4051 °F)
Bylin pynt	4876 K ​(4603 °C, ​8317 °F)
Density (near r.t.)	13.31 g/cm3
when liquid (at m.p.)	12 g/cm3
Heat o fusion	27.2 kJ/mol
Heat o vapourisation	571 kJ/mol
Molar heat capacity	25.73 J/(mol·K)
Vapour pressur P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 2689 2954 3277 3679 4194 4876
Atomic properties
Oxidation states	−2, +1, +2, +3, +4 (an amphoteric oxide)
Electronegativity	Pauling scale: 1.3
Atomic radius	empirical: 159 pm
Covalent radius	175±10 pm
Spectral lines o hafnium
Ither properties
Naitural occurrence	Hf: Primordial
Creestal structur	​hexagonal close-packed (hcp)
Speed o soond thin rod	3010 m/s (at 20 °C)
Thermal expansion	5.9 µm/(m·K) (at 25 °C)
Thermal conductivity	23.0 W/(m·K)
Electrical resistivity	331 n Ω·m (at 20 °C)
Magnetic orderin	paramagnetic
Young's modulus	78 GPa
Shear modulus	30 GPa
Bulk modulus	110 GPa
Poisson ratio	0.37
Mohs haurdness	5.5
Vickers haurdness	1760 MPa
Brinell haurdness	1700 MPa
CAS Nummer	7440-58-6
History
Prediction	Dmitri Mendeleev (1869)
Diskivery	Dirk Coster an George de Hevesy (1922)
First isolation	Dirk Coster an George de Hevesy (1922)
Main isotopes o hafnium
Iso­tope Abun­dance Hauf-life (t1/2) Decay mode Pro­duct 172Hf syn 1.87 y ε 172Lu 174Hf 0.162% 2×1015 y α 170Yb 176Hf 5.206% - (α) 172Yb 177Hf 18.606% - (α) 173Yb 178Hf 27.297% - (α) 174Yb 178m3Hf syn 31 y IT 178Hf 179Hf 13.629% - (α) 175Yb 180Hf 35.1% - (α) 176Yb 182Hf trace 8.9×106 y β− 182Ta
Decay modes in parentheses are predictit, but hae nae yet been observed

Hafnium is a chemical element wi the seembol Hf an atomic nummer 72. A lustrous, sillery gray, tetravalent transeetion metal, hafnium chemically resembles zirconium an is foond in zirconium minerals. Its existence wis predictit bi Dmitri Mendeleev in 1869. Hafnium wis the penultimate stable isotope element tae be discovered (rhenium wis identified twa year later). Hafnium is named efter Hafnia, the Latin name for Copenhagen, whaur it wis discovered.