When Oganov and his colleagues began exploring how noble gases would behave under pressure, they started with an element that no one had observed as a compound—helium. Computations suggested that a reaction with fluorine was most likely, so Oganov asked his graduate student Xiao Dong to give it a try. So Oganov told Dong to abandon the project.
Structure of Na 2 He at high pressure. Sodiums are the purple spheres, heliums are the green cubes, and electrons are the red regions. Credit: Artem Oganov.
The finding was completely counterintuitive, Oganov says. Oganov and colleagues predict that the compound Na 2 OHe might be stable at pressures as low as 15 GPa, which is in the neighborhood of the amount of pressure used to convert graphite to diamonds. More by Bethany Halford.
Cite this: ACS Cent. ACS AuthorChoice. Article Views Altmetric -. Author Information. Cited By. This article has not yet been cited by other publications. Abstract High Resolution Image. Pair your accounts. Your Mendeley pairing has expired. Please reconnect. Because the noble gases are the least reactive of all elements, their eight valence electrons are used as the standard for non-reactivity, and to explain how other elements interact. This is stated as the octet "group of eight" rule.
According to this rule, atoms react to form compounds that allow them to have a group of eight valence electrons like the noble gases. For example, sodium with one valence electron reacts with chlorine with seven valence electrons to form the stable compound sodium chloride table salt.
In this reaction, sodium donates an electron and chlorine accepts it, giving each element an octet of valence electrons. Have you ever had helium balloons like those in the elephant image? Unlike a balloon filled with air, a balloon filled with helium needs to be weighted down so that it won't float away—although you don't have to use an elephant! Early incandescent light bulbs, like the one pictured in the figure below, didn't last very long.
The filaments quickly burned out. Although air was pumped out of the bulb, it wasn't a complete vacuum. Oxygen in the small amount of air remaining inside the light bulb reacted with the metal filament. This corroded the filament and caused dark deposits on the glass.
Filling a light bulb with argon gas prevents these problems. That's why modern light bulbs are filled with argon. Noble gases are also used to fill the glass tubes of lighted signs like the one in the figure below. Although noble gases are chemically nonreactive, their electrons can be energized by sending an electric current through them.
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