Discovery of Hafnium: Impact on Chemistry and Technology

Hevesy George Charles von's discovery of hafnium in 1923, alongside Dirk Coster, was a milestone in chemistry, adding significant depth to our understanding of the periodic table. Hafnium, with the atomic number 72, was one of the last elements predicted by Dmitri Mendeleev's periodic table to be found in nature. Its discovery confirmed the accuracy of Mendeleev's predictions and filled a critical gap, validating the periodic law.

Hafnium is named after "Hafnia," the Latin name for Copenhagen, where Hevesy and Coster made their discovery. The journey to identifying hafnium was not straightforward. Despite numerous efforts, the element eluded detection because it closely resembled zirconium, making it difficult to separate from its chemically similar counterpart. The breakthrough came with the use of X-ray spectroscopy, a technique that allowed Hevesy and Coster to distinguish hafnium from zirconium by its unique spectral lines.

This discovery had significant implications for both theoretical and applied chemistry. Hafnium is found in zirconium ores, such as zircon, and typically occurs in a concentration of about 1-5% relative to zirconium. Its chemical properties are so similar to zirconium that the two elements are often found together in nature and are difficult to separate. However, hafnium has unique characteristics that make it invaluable in various high-tech applications.

Hafnium's most notable property is its ability to absorb neutrons, which makes it extremely valuable in nuclear reactors. It is used in control rods that regulate the fission process, ensuring the safe operation of nuclear power plants. This neutron-absorbing capability also makes hafnium essential in the manufacture of nuclear submarines and other nuclear-powered vessels.

Beyond nuclear applications, hafnium's high melting point and corrosion resistance make it a key component in high-temperature alloys and ceramics. These materials are crucial for the aerospace industry, where they are used in jet engines and spacecraft, as well as in plasma cutting tools and other advanced manufacturing technologies.

In recent years, hafnium has found a place in the semiconductor industry. Hafnium dioxide (HfO₂) is used as an insulator in field-effect transistors (FETs) for modern microprocessors and memory devices. Its superior insulating properties enable the continued miniaturization of electronic components, supporting the development of faster and more efficient computers and other electronic devices.

Hevesy's and Coster's discovery of hafnium thus not only filled a critical gap in the periodic table but also paved the way for advancements in numerous fields, from nuclear energy to aerospace and electronics. This discovery exemplifies the profound impact that fundamental scientific research can have on technology and industry.
Discovery of Hafnium: Impact on Chemistry and Technology

Discovery of radium and polonium

In 1891 Maria Sklodowska (1867-1934) moved to Paris from her native Poland to undertake scientific studies. In 1895 she married Pierre Curie (1859-1906), a physicist renowned for his work on magnetism and his theory on symmetry in physical phenomena.

Marie started work in Pierre’s laboratory in Rue Lhomond, Paris, using pitchblende uranium ore from the Joachimstal mine in Poland, at that time ruled by Austria. She tried to identify which substances and minerals besides pitchblende could also emit ionizing radiation.

Marie Curie developed an apparatus, the electroscope, for measuring radioactivity more accurately, as the photographic plate method was too crude.

Pierre Curie joined her in her research. To their surprise, the radioactivity of some of the ores were three to four times greater than could be accounted for on the basis of just their uranium and thorium content.

Marie treated the ore and, following Fresenius chemistry methodology, she separated several salt fractions and measured the radioactivity in each fraction. The Curies decided they had found a new element since, although the sample was far from pure, it was far more radioactive than either U or Th. They called it polonium (after Poland, Marie’s native country).

The symbol Po is written for the first time in the laboratory note book on 13 July 1893 by the hand of Pierre Curie. The article published in the Comptesrendus de l’ Académie des Sciences announces the discovery of a new element, more radioactive than uranium, but not seen as yet.

In the physical and chemical separation procedure applied to treat the uranium ore, they observed also high radiation emission in another chemical fraction containing barium. They hypothesized that eventually other substance with a chemical behavior close to barium could be present. Unlike uranium and polonium, radium does not occur freely in nature, the Curies and their assistant Andre were able to extract about 1 milligram of radium from nearly 10 tons of pitchblende in 1902.

The Curies wrote: “There is a strong reason to believe that the substance obtained contains a new element. We propose to name it as Radium. This new radioactive substance obtained probably still contains a large amount of barium mixed therein, but radium radioactivity seems enormous”. The Curies and their assistant Andre were able to extract about 1 milligram of radium from nearly 10 tons of pitchblende, according to the Royal Society of Chemistry.

Pure radium was isolated in 1902 by electrolysis by Marie Curie and Andre Debierne, a French chemist, according to New World Encyclopedia.
Discovery of radium and polonium