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So, who discovered nobelium?

Electron shell diagram for nobelium – element number 102 with the atomic symbol No.   | Photo Credit: Pumbaa/Wikimedia Commons

The discovery of a number of trans-uranium elements – elements heavier and with an atomic number greater than that of uranium (92), the heaviest naturally stable element – has been contested with parallel claims from different groups of scientists. Apart from the bragging rights that comes from being the discoverers, it also gives them the priority to name the element, forever leaving their trace in the periodic table. Among these tales, nobelium’s discovery could be the most complicated and it was eventually resolved only after decades.

Swedes start it

Nobelium is a synthetic element, meaning that it doesn’t exist naturally on the Earth’s surface. A number of isotopes of this element have now been produced, but much still remains unknown. With the longest-lived isotope having a half-life of 58 minutes, nobelium has no practical applications and is limited to scientific research.

The story of nobelium’s discovery begins in 1957. For it was on July 9 that year that scientists from the Nobel Institute of Physics in Stockholm, Sweden announced the discovery of element 102, naming it nobelium. They claimed that they had produced an isotope of the element with a half-life of 10 minutes by bombarding curium with carbon in a cyclotron. The announcement found its way to the front page of The New York Times the next day, as it did correspond to the heaviest human-made element at that time.

Americans continue

American nuclear scientist Albert Ghiorso and his team, working at the Lawrence Radiation Laboratory (now Lawrence Berkeley Laboratory), however, weren’t able to replicate the Swedish discovery. They did produce a different isotope of element 102 in 1958, when they also bombarded curium with carbon. This isotope had a half-life of just three seconds.

A third group of scientists, based out of the Joint Institute for Nuclear Research, Dubna, Russia, stepped into the frame next. Under the leadership of Soviet nuclear physicist Georgy Flerov, this group was also unable to reproduce the Swedish work, but was able to repeat the Berkeley group’s effort. They spent much of the 1960s producing more isotopes of the element, recording their observations in great detail.

Russians get the official nod

This marked the beginning of a wrangling that would stretch for decades over who actually discovered element number 102. While the Swedish side stepped away when they realised that none of nobelium’s isotopes has a half-life of 10 minutes, Ghiorso and Flerov were at loggerheads with each other, and were unable to amicably settle their disagreement.

The International Union of Pure and Applied Chemistry (IUPAC) had to eventually step in, and they couldn’t come up with an immediate answer either. After reassessing the claims of discovery for nobelium, it was only in the 1990s that they finally gave their verdict. They concluded that only the Dubna team’s work from 1966 correctly detected and assigned decays to nuclei of element 102. Flerov’s team is therefore officially recognised as nobelium’s discoverers, even though Ghiorso’s group might have detected it first.

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A name that lives on

Swedish chemist, inventor and philanthropist, Alfred Nobel held hundreds of patents during his lifetime, with the invention of dynamite being his most famous work.

His name, however, is now more often associated with the Nobel Prizes, which he founded. He also left much of his fortune towards running these prizes.

While his works have ensured that his name lives on, it was also honoured by chemists when the element 102 was named after him. It was scientists from the Nobel Institute in Sweden who had suggested the name nobelium (No).

Even though their experiment was discredited, the name they had suggested stayed on. This wasn’t to say, however, that it wasn’t contested. The Soviets proposed the name joliotium, either after French physicist Frederic Joliot-Curie or his wife Irene Joliot-Curie, in the 1960s, creating a naming controversy. The IUPAC proposed the name flerovium (Fl) in the 1990s, but it wasn’t accepted either and the name nobelium was restored. Element 114 is now named flerovium (Fl).

The fact that the name nobelium was by now entrenched in public memory and honoured Nobel, along with its widespread use in scientific literature were contributing factors towards retaining the name.

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Printable version | May 8, 2021 7:07:30 AM | https://www.thehindu.com/children/so-who-discovered-nobelium/article28227073.ece

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