Nuno A. G. Bandeira, Principal Investigator at the Chemistry for Biological Systems Research Group, BioISI – Ciências ULisboa, is the first author of a new paper published in the Physical Chemistry – Chemical Physics Journal by the Royal Society of Chemistry, where different radon and xenon [two noble gases] complexes were studied and their bonding, vibrational and energetic properties analyzed. Read the BioISI Digest below to find out more about this investigation. 

What was the starting point that led to the current research?

The idea was to probe quantum chemically into the possible existence and stability with regard to the decomposition of radon tetroxide (RnO₄). Xenon tetroxide is already well known and is an explosive gas that decomposes pyrophorically [i.e. spontaneous ignition in air at a given temperature] into elemental Xe and O₂. It was curious to see whether the radon analogue would behave similarly in spite of the element’s radioactivity.

What is the main finding reported in this paper?

It was found that indeed RnO₄ is even less stable than its xenon congener. The reason for this lies in what is known as the ‘inert pair effect’, a principle initially laid out by Neville Sidgwick in 1933 (Sidgwick, N.V., The “Inert Pair” of Valency Electrons. Ann. Rep. Prog. Chem., 1933. 30: p. 120-128) to account for the empirical observation of the lesser thermodynamic stability of high-valent period 6 elements (Tl^III,Pb^IV,Bi^V). In the late 1960s, it was shown that the reason for this is due to the relativistic stabilization of the electronic s-shell in these elements. Heretofore it was an open question whether this inert pair effect would be extended to cover the remaining elements of the 6^th period (Po, At, Rn). In this paper, we demonstrate clearly that radon does manifest the inert pair effect in its chemistry and consequently, it is also likely to be present in polonium and astatine.

Why is it important for the scientific community and for society at large?

The understanding of radon chemistry is relevant due to its presence in geogenic emissions and in stone-encased building structures (https://apambiente.pt/prevencao-e-gestao-de-riscos/radao ). The motivation for this research was entirely curiosity driven but its impact may be felt in the long run when creating radiation gas disposal technologies.

What are the next steps?

This research was conducted under the auspices of an FCT project (PTDC/QUI-QFI/31896/2017) that came to an end last year. There are some aspects that I would like to explore further particularly the low-valent chemistry of radon peroxides and monoxides or gas phase ions. An experimental partner (Joaquim Marçalo) is attempting to obtain a radium chloride sample (the radionuclide precursor of radon gas) to conduct some mass spectrometric experiments with radon and generate some ionic species in the gas phase.

Discover more about CBS Group here.

Get to know Nuno A. G. Bandeira’s research here.

Read the full paper here.

Nuno Bandeira [photo provided by the researcher]