JUN 07, 2019 6:00 AM PDT

Reactions Impossible: How Chemists Strived to Make Noble Gas Compounds

WRITTEN BY: Daniel Duan

Electric discharge of noble gases (Wikimedia Common)

Translated from the German word Edelgas, noble gases commonly refer the six elements occupying the rightmost column of the periodic table: helium,  helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).

Take argon for example, ever since its discovery in 1894 chemists had tried various methods, such as heating and electric sparks, to make it react with fluorine the most reactive gas in the early twentieth century. However, no one succeeded. According to the electron shell theory, argon atoms, like other noble gases, have full outer shells of electrons, and it would take certain extreme conditions to force them to share their electrons with other atoms to form bonds.

Nobel laureate and revered chemist Linus Pauling collaborated with his Caltech colleague Don Yost, who tried to get xenon to react with fluorine. Despite a lot of efforts, the only thing Yost obtained at the end of his experiments was corroded quartz flasks with not even a drop of any new compound inside.

Thanks to British Chemist Neil Bartlett, the first noble gas compound xenon hexafluoroplatinate, or Xe(PtF6), was finally synthesized in the 1960s. But it is so unstable that it could not be used for any purpose. The instability was also observed in other noble gases-based compounds.

Therefore, it has long been considered ill-advised for a chemist to build his or her research projects around noble gases. However, these inert elements represent irresistible attraction because they harbor new chemical mechanisms which can lead to brand new compounds with otherworldly properties.

In recent years, much progress has been made in noble gas chemistry. An international group of chemists managed to produce a stable helium-based compound with sodium, a highly reactive metal. To make the reaction happen, researchers had to compress the reaction to 113 GPa, which is close to a million times Earth’s atmospheric pressure. The resulted product, disodium helide (Na2He), has a fluorite-like structure and was reported to be stable at the same pressure of the reaction.

Canadian researchers from McMaster University explored ways to enhance the stability of noble gas-based compounds. Xenon trioxide (XeO3) is a strong oxidizer which can explode upon exposure to water or sunlight. The McMaster team forced XeO3 to coordinate with 15-crown-5, a crown-like ether molecule that can form reversible bonds with the xenon atom. The resulted complex is stable at room temperature.

As more scientists are joining the exploration, we can look forward to more previously-unknown chemistry hidden within the group of most inert of elements. 

Find out more interesting stories about noble gases such as xenon in the following video by Thoisoi2.

Xenon - THE BRIGHTEST Gas on Earth! (Thoisoi2 - Chemical Experiments!)

Source: C&EN

About the Author
Master's (MA/MS/Other)
Graduated with a bachelor degree in Pharmaceutical Science and a master degree in neuropharmacology, Daniel is a radiopharmaceutical and radiobiology expert based in Ottawa, Canada. With years of experience in biomedical R&D, Daniel is very into writing. He is constantly fascinated by what's happening in the world of science. He hopes to capture the public's interest and promote scientific literacy with his trending news articles. The recurring topics in his Chemistry & Physics trending news section include alternative energy, material science, theoretical physics, medical imaging, and green chemistry.
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