Hafnium

> **Atomic Weight:** 178.49 > **Melting Point:** 2506 K (2233°C or 4051°F) > **Boiling Point:** 4876 K (4603°C or 8317°F) > **Density:** 13.3 grams per cubic centimeter > **Phase at Room Temperature:** Solid > **Element Classification:** Metal > **Period Number:** 6 **Group Number:** 4 **Group Name:** none > **Say what?** Hafnium is pronounced as **HAF-neeem**. > **History and Uses:** > Hafnium was discovered by Dirk Coster, a Danish chemist, and Charles de Hevesy, a Hungarian chemist, in 1923. They used a method known as X-ray spectroscopy to study the arrangement of the outer electrons of atoms in samples of zirconium ore. The electron structure of hafnium had been predicted by Niels Bohr and Coster and Hevesy found a pattern that matched. Hafnium is difficult to separate from zirconium and is present in all of its ores. It is obtained with the same methods used to extract zirconium. > Hafnium is a good absorber of neutrons and is used in the control rods of nuclear reactors. Hafnium is also used in vacuum tubes as a getter, a material that combines with and removes trace gases from vacuum tubes. Hafnium has been used as an alloying agent in iron, titanium, niobium and other metals. > Melting near 3890°C, hafnium carbide (HfC) has the highest melting point of any known two-element compound. Hafnium nitride (HfN) also has a high melting point, around 3305°C. Other hafnium compounds include: hafnium chloride (HfCl4), hafnium fluoride (HfF4) and hafnium oxide (HfO2). > **Estimated Crustal Abundance:** 3.0 milligrams per kilogram > **Estimated Oceanic Abundance:** 7×10-6 milligrams per liter > **Number of Stable Isotopes:** 5 (View all isotope data) > **Ionization Energy:** 6.825 eV > **Oxidation State:** +4 Hafnium is used for alloying with iron, titanium, niobium and other metals. The metal is used for nuclear control rods and is an efficient "getter" for scavenging oxygen and nitrogen. It is used in gas-filled and incandescent lamps. Brief description: most zirconium minerals contain 1 to 3% hafnium. Hafnium is a ductile metal with a brilliant silver lustre. Its properties are influenced considerably by the impurities of zirconium present. Of all, zirconium and hafnium are two of the most difficult to separate. Hafnium is a Group 4 transition element. Because hafnium has a good absorption cross section for thermal neutrons (almost 600 times that of zirconium), has excellent mechanical properties, and is extremely corrosion resistant, it is used for nuclear reactor control rods. Hafnium carbide is the most refractory binary composition known, and the nitride is the most refractory metal nitride (m.p. 3310°C).
 * Name: Hafnium
 * Atomic Number: 72
 * Atomic Weight: 178.49 (2)
 * Standard Sate: solid at 298 K
 * CAS Registry: 7440-58-6
 * Group: 4
 * Group Name: (none)
 * Period: 6
 * Block in periodic table: d-block
 * Color: grey steel
 * **Atomic Number:** 72
 * What's in a name?** From the Latin word for the city of Copenhagen, **Hafnia**.
 * Uses**

Isolation: hafnium extraction is always associated with its removal from zirconium as it is a contaminant of all zirconium minerals. Solvent extraction methods are used ot spearate the two metals but the process is not easy. These make use of the differential solubilities of the metal thiocyantes (thiocyanate is SCN-) in methyl isobutyl ketone.

a [|chemical element] with the [|symbol] **Hf** and [|atomic number] 72. A [|lustrous], silvery gray, [|tetravalent] [|transition metal], hafnium chemically resembles [|zirconium] and is found in zirconium [|minerals]. Its existance was [|predicted by Dmitri Mendeleev] in 1869. Hafnium was the penultimate [|stable isotope] element to be discovered ([|rhenium] was identified two years later). Hafnium is named for //Hafnia//, the [|Latin] name for "[|Copenhagen]", where it was discovered. Hafnium is used in filaments and electrodes. Some [|semiconductor] fabrication processes use its oxide for [|integrated circuits] at 45 nm and smaller feature lengths. Some [|superalloys] used for special applications contain hafnium in combination with [|niobium], [|titanium], or [|tungsten]. Hafnium's large [|neutron capture] cross-section makes it a good material for [|neutron] absorption in [|control rods] in [|nuclear power plants], but at the same time requires that it be removed from the neutron-transparent corrosion-resistant zirconium alloys used in nuclear reactors.


 * Symbol:** Hf **Atomic Number:** 72 **Atomic Mass:** 178.49 amu **Melting Point:** 2150.0 °C (2423.15 K, 3902.0 °F) **Boiling Point:** 5400.0 °C (5673.15 K, 9752.0 °F) **Number of Protons/Electrons:** 72 **Number of Neutrons:** 106 **Classification:** Transition Metal **Crystal Structure:** Hexagonal **Density @ 293 K:** 13.2 g/cm3 **Color:** Silver

Atomic Structure

 * [[image:http://www.chemicalelements.com/bohr/b0072.gif width="355" height="353"]] ||  || **Number of Energy Levels:** 6
 * First Energy Level:** **Second Energy Level:** **Third Energy Level:** **Fourth Energy Level:** **Fifth Energy Level:** **Sixth Energy Level:** ||

Isotopes

 * ** Isotope ** || ** Half Life ** ||
 * Hf-172 || 1.9 years ||
 * Hf-174 || 2.0E15 years ||
 * Hf-175 || 70.0 days ||
 * Hf-176 || Stable ||
 * Hf-177 || Stable ||
 * Hf-178 || Stable ||
 * Hf-179 || Stable ||
 * Hf-180 || Stable ||
 * Hf-182 || Stable ||
 * Hf-182 || Stable ||

Facts

 * Date of Discovery:** 1923 **Discoverer:** Dirk Coster **Name Origin:** From the Latin word Hafnia (Copenhagen) **Uses:** nuclear reactors **Obtained From:** zircon