What are the noble gases? The noble gas group consists of the elements helium (He), neon (Ne), argon, (Ar), krypton (Kr), xenon, radon (Rn), and organesson (Og). It is the 18th (7A) group in the periodic table of elements. They are known to be odourless, tasteless, colourless, and non-flammable under standard conditions. They are called noble gases because they are already stable, unlike the other elements in the periodic table. They do not create bonds with other atoms to produce new chemical compounds.
Before, these gases are called rare or inert gases. However, it is also found that some of these elements are very abundant in our universe. Because calling them “rare” or “inert” was misleading, the word “noble” was introduced.
Noble gas: Argon and its history
Argon has an atomic number of 18 and an atomic weight of 39.948 atomic mass unit. About 0.93% of the Earth’s atmosphere is occupied by argon. It is a very abundant gas in the air, next to nitrogen and oxygen. From the production of oxygen and nitrogen, argon gas is produced as a by-product. You can also find small traces of argon in Earth’s crust and ocean waters. Argon is the most abundant and cheapest noble gas. Stable isotopes of argon are argon-36, and argon-38 and argon-40. Argon-36 is created by stars and the most common in the universe while over 99% of argon that occurs naturally on Earth is the argon-40.
Lord Rayleigh, an English chemist, and Sir William Ramsay, a Scottish chemist, discovered the argon gas in 1894. It is derived from the Greek word “argos”, meaning idle. However, before argon was fully discovered, Henry Cavendish, an English chemist and physicist, found a chemically less active substance than nitrogen, which is about 1% proportion of air. Then, Lord Rayleigh tried to isolate nitrogen from the air after a century, but it was not pure nitrogen that he isolated as he thought. He discovered that the element has a higher density than nitrogen. Then finally, in 1894, Sir William Ramsay started working with Lord Rayleigh. They collaborated to isolate this gas. After a series of trials and experiments, they proved that they had discovered a new element: argon.
The chemical reactivity of argon
Fluorine is also an element in the periodic table, considered the most reactive element. A French chemist, Henri Moissan, discovered fluorine in 1886. He was also the one who attempted to produce a reaction between argon and fluorine, but he failed.
According to Niels Bohr in 1913, electrons’ distribution in an atom is arranged in successive shells. In the electron configuration, the ideal number of electrons in the atom’s outermost shell must be eight, hence the octet rule. It is the reason why most atoms need to bond with other atoms, except for noble gases. These gases already have eight electrons in their valence or outer shell, making them the most stable gases.
Although argon is considered inert and already stable, it is also discovered that it can form at least one compound: argon fluorohydride (HArF). Leonid Khriachtchev, Mika Pettersson, Nino Runeberg, Jan Lundell, and Markku Räsänen reported this discovery in August 2000. The said compound is only stable at very low temperatures. If the temperature increases, argon fluorohydride tends to decompose. For this reason, the compound has no use in basic scientific research.