{"id":68,"date":"2020-04-08T15:01:13","date_gmt":"2020-04-08T15:01:13","guid":{"rendered":"https:\/\/thechemicalelements.com\/?page_id=68"},"modified":"2023-08-16T10:12:58","modified_gmt":"2023-08-16T10:12:58","slug":"hafnium","status":"publish","type":"post","link":"https:\/\/thechemicalelements.com\/hafnium\/","title":{"rendered":"Hafnium (Hf)"},"content":{"rendered":"\n

Hafnium is a chemical element with an atomic number of 72 in the periodic table of elements. It makes up about\u00a0 3.3 parts per million (ppm) of Earth’s crust. However, it does not exist in its free metallic form in nature. This tetravalent transition metal is characterized as the most refractory of all nitrides of metals.\u00a0<\/span><\/p>\n\n\n\n

<\/div>\n\n\n\n

Chemical and Physical Properties of Hafnium<\/span><\/h2>\n\n\n\n
Property<\/strong><\/td>Value<\/strong><\/td><\/tr>
The symbol in the periodic table of elements<\/td>Hf<\/td><\/tr>
Atomic number<\/td>72<\/td><\/tr>
Atomic weight (mass)<\/td>178.49 g.mol-1<\/td><\/tr>
Group number<\/td>4 (Transition elements)<\/td><\/tr>
Period<\/td>6<\/td><\/tr>
Color<\/td>A lustrous and bright silvery metallic substance<\/td><\/tr>
Physical state<\/td>Solid metal at room temperature<\/td><\/tr>
Half-life<\/td>From 400# ms [>200 ns] to 2.0(4)\u00d710^15 years<\/td><\/tr>
Electronegativity according to Pauling<\/td>1.3<\/td><\/tr>
Density<\/td>13.07 g.cm-3 at 20\u00b0C<\/td><\/tr>
Melting point<\/td>2200\u00b0C<\/td><\/tr>
Boiling point<\/td>5200\u00b0C<\/td><\/tr>
Van der Waals radius<\/td><\/td><\/tr>
Ionic radius<\/td>0.075 nm<\/td><\/tr>
Isotopes<\/td>32 (5 stable isotopes)<\/td><\/tr>
Most characteristic isotopes<\/td>177Hf, 178Hf, 180Hf<\/td><\/tr>
Electronic shell<\/td>[Xe] 4f145d26s2<\/td><\/tr>
The energy of the first ionization<\/td>530 kJ.mol-1<\/td><\/tr>
The energy of the second ionization<\/td>1425.5 kJ.mol-1<\/td><\/tr>
The energy of the third ionization<\/td>2244.3 kJ.mol-1<\/td><\/tr>
Discovery date<\/td>In 1923 by Georg von Hevesy and Dirk Coster<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

The chemical structure of this element is almost identical to the one of zirconium<\/a>. With the periodic table symbol Hf, atomic number 72, atomic mass of 178.49 g.mol<\/span>-1<\/span>, and electron configuration X, actinium<\/a> is a corrosion-resistant and ductile metal that reaches its boiling point at 5200\u00b0C, while the melting point is achieved at 2200\u00b0C. <\/span><\/p>\n\n\n\n

This member of the transition metals family of elements in the periodic table has an electronegativity of 1.3 according to Pauling, whereas the atomic radius according to van der Waals is 0.161 nm. <\/span><\/p>\n\n\n\n

As a result of the oxide film formation on its exposed surfaces, hafnium possesses strong anti-corrosive qualities. This transition metal is not reactive with water molecules, air, alkalis and acids, but readily reacts with hydrogen<\/a> fluoride. The powder form of hafnium spontaneously ignites, i.e. it has a pyrophoric property.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><\/p>\n\n\n\n

<\/div>\n\n\n\n

How Was Hafnium Discovered?<\/span><\/h2>\n\n\n\n

Hafnium is one of the chemical elements predicted by Dmitri Mendeleev in 1869. Several decades before hafnium was introduced to the world of chemistry, Mendeleev postulated the existence of element 72. This chemical was supposed to be heavier than zirconium and titanium<\/a>, and fall between element 71 (lutetium<\/a>) and element 73 (tantalum<\/a>).\u00a0<\/span><\/p>\n\n\n\n

<\/div>\n\n\n\n

Georges Urbain\u2019s Breakthrough Analysis<\/span><\/h3>\n\n\n\n

In 1911, the French chemist and discoverer of the rare earth element lutetium Georges Urbain (1872 – 1938) thought that he was on the way to discovery of the missing element as predicted by Mendeleev. Upon conducting his spectral analysis of rare-earth elements, Urbain recognized the properties of the missing element in the result of his experiment. On that occasion, he labeled the newly discovered substance as <\/span>celtium<\/span><\/i>.<\/span><\/p>\n\n\n\n

However, several years after what he believed was a monumental discovery, additional analysis of the chemical proved that it was merely a compound of already discovered lanthanides. While attempting a more thorough research on the subject,\u00a0 the English chemist Henry Moseley (1887 – 1915) performed an X-ray spectroscopy. This led him to scientific evidence that proved Georges Urbain’s element \u2018celtium\u2019 was not element 72.<\/span><\/p>\n\n\n\n

<\/div>\n\n\n\n

Niels Bohr\u2019s Postulate <\/span><\/h3>\n\n\n\n

Since it was not clear whether this elusive element\u00a0 could be classified as a transition metal or a rare-earth metal, Danish physicist Niels Bohr (1885 – 1962) proposed the missing element to be included among the transition metals. Bohr, who is also one of the founders of quantum theory, based his postulate upon the basis of the electron configuration of the element that we know today as hafnium.\u00a0<\/span><\/p>\n\n\n\n

<\/div>\n\n\n\n

Georg von Hevesy and Dirk Coster\u2019s Contribution to the Discovery <\/span><\/h3>\n\n\n\n

In order to support his postulate, he assigned the Hungarian chemist Georg von Hevesy and the Dutch physicist Dirk Costerto to attempt to isolate the element as a confirmation to his theory. For this reason, the two scientists employed at Bohr’s institute performed a scrutinized research of the mineral zircon via an X-ray spectroscopic analysis. The result of their extensive scientific efforts proved that the zirconium ore contained the missing element 72, which was later named hafnium (Hf).<\/span><\/p>\n\n\n\n

<\/div>\n\n\n\n

The High-Purity Hafnium Production Method<\/span><\/h3>\n\n\n\n

In 1925, the Dutch chemists Anton Eduard van Arkel and Jan Hendrik de Boer managed to produce high-purity hafnium by decomposing hafnium tetraiodide over a heated tungsten filament. This resulted in a crystal bar of pure hafnium.\u00a0<\/span><\/p>\n\n\n\n

<\/div>\n\n\n\n

How Did Hafnium Get Its Name?<\/span><\/h2>\n\n\n\n

The Latin word for Copenhagen \u2018<\/span>Hafnia<\/span><\/i>\u2019 served as a label of the new element. Copenhagen was both the city where hafnium was first isolated, and the hometown of Niels Bohr – one of the one of the founders of quantum theory and the scientist who encouraged hafnium\u2019s discoverers to conduct the revolutionary analysis of the zirconium ore.\u00a0<\/span><\/p>\n\n\n\n

<\/div>\n\n\n\n

Where Can You Find Hafnium?<\/span><\/h2>\n\n\n\n

Element 72 is relatively scarce in nature and difficult to be produced. Hafnium metal can be rarely found in nature in its pure form. It mostly occurs in compounded form with thortveitite, and alvite [(Hf, Th, Zr) SiO<\/span>4<\/span> H<\/span>2<\/span>O]. However, zircon (ZrSiO<\/span>4<\/span>) is the primary source of hafnium.  For the use in the nuclear, chemical, and aerospace industries, this chemical is obtained as a byproduct during the refinement of zirconium. <\/span><\/p>\n\n\n\n

Not only was hafnium found in many zirconium minerals, but it also resembled the chemical structure of zirconium. This made element 72 difficult to isolate it in its pure elemental form and the process would take a long time.<\/span><\/p>\n\n\n\n

<\/div>\n\n\n\n

Hafnium in Everyday Life<\/span><\/h2>\n\n\n\n

Despite being not so evident in our everyday life, hafnium is commonly used in the electronics and nuclear power industries:<\/span><\/p>\n\n\n\n