Scientists breakthrough in demystification of Einsteinium

Sankar Ray

Seventy years after the identification and christening the highly radioactive element at the bottom of ‘Periodic Table’, Einsteinium (Es), a group of scientists in a globally collaborative research project, measured it, thus, finally providing a close look at its chemical properties and behaviour. It sheds light into the  radioactive metal and other so-called transplutonium elements that occupy the fringes of the Periodic Table.  World’s topmost scientific journal posted the paper online on 3 February, captioned,’ Structural and spectroscopic characterization of an Einsteinium complex’. The lead author of the 12-member team is Korey P. Carter, professor  of chemistry at the University of Iowa. "It is a very small amount of material. You can't see it, and the only way you can tell it is there is from its radioactive signal,” he stated, when questioned by Live Science .  Einsteinium  was created in a 1952 hydrogen bomb test in 1952 on the island of Elugelab, now a part of the Marshall Islands in the Pacific Ocean, and named after Albert Einstein in the fag end of his life. Such heavy, radioactive elements like  Einsteinium and Californium as also  Uranium and Plutonium belong to  the actinide group: elements 89 to 103 on the Periodic Table. Einsteinium and Californium are few elements that are synthesised.

This breakthrough happened in the centenary of award of Nobel Prize in physics to Einstein -"for his services to theoretical physics, and especially for his discovery of the law of the photoelectric effect”. Pathetically enough, he didn’t receive the prize for his General Theory of Relativity which was l considered somewhat controversial as the idea of photons was considered outlandish and hindered universal acceptance until the 1924 when the Indian theoretical physicist Satyendra Nath Bose – famous for Bose-Einstein Statistics - achieved  derivation of the Planck spectrum.  

 “The transplutonium elements (atomic numbers 95–103) are a group of metals that lie at the edge of the periodic table. As a result, the patterns and trends used to predict and control the physics and chemistry for transition metals, main-group elements and lanthanides are less applicable to transplutonium elements. Furthermore, understanding the properties of these heavy elements has been restricted by their scarcity and radioactivity. This is especially true for einsteinium (Es), the heaviest element on the periodic table that can currently be generated in quantities sufficient to enable classical macroscale studies”, states the abstract of the paper.
  
All actinides are highly radioactive and mostly untraceable in nature. When atoms get very big alike actinides it becomes difficult for chemists to predict how they will  behave since  they have so many sub-atomic particles with opposing charges, barely held together.

For example, the particles around the outside of an atom are the negatively charged electrons, the outermost of which are called valence electrons. The number of valence electrons that an atom has determines how many other atoms it can form bonds with. And Einsteinium is so big that it is  hard to predict its valence value. Those paper broke through by measuring it.

“This quantity is of fundamental importance in chemistry, determining the shape and size of the building blocks from which the universe is made,” according to Keele University chemist Robert Jackson. “Einsteinium happens to lie at an ambiguous position on the periodic table, between valence numbers, so establishing its valence helps us understand more about how the periodic table should be organized”, he added.

The researchers were working with a mere 200 nanograms of Es, an amount about 300 times lighter than a grain of salt. States Korey Carter, a microgram (1,000 nanograms) was previously thought to be the lower limit for a sample size. ‘There were questions of, ‘Is the sample going to survive?’ that we could prepare for as best as we possibly could, Amazingly, amazingly, it worked’, he responded in a video call.

The team got their Es from the Oak Ridge National Laboratory’s High Flux Isotope Reactor which normally makes californium, used for detecting gold and silver. Californium and Einsteinium have a lot in common, the latter is often a by-product of californium production. Nonetheless, it was tough to separate them. So the lab only got a very small sample of Es—about 200 billionths of a gram. But even then, it was too contaminated with californium to conduct some of their tests. The solution emerged when the team bombarded  it with high-energy light using the Stanford Synchrotron Radiation Light source in order to take measurements. In one of the findings, the team found that while most actinides reflect a longer wavelength than the light shot at them, Einsteinium does the opposite, and reflects shorter wavelengths. It also found that when other elements bonded to Einsteinium, the bonds were slightly shorter than they’d predicted. Then it was possible to measure the bond distance of Einsteinium-254 using X-ray absorption spectroscopy.  Einsteinium-254 has a half-life of 276 days, meaning it takes 276 days for half of the material to decay.

Frontier
Feb 11, 2021