Argon's complete octet of electrons indicates full s and p subshells.
This full valence shell makes argon very stable and extremely resistant to bonding with other elements.
Before 1962, argon and the other noble gases were considered to be chemically inert and unable to form compounds; however, compounds of the heavier noble gases have since been synthesized.
The first argon compound with tungsten pentacarbonyl, W(CO)₅Ar, was isolated in 1975.
However it was not widely recognised at that time.
In August 2000, another argon compound, argon fluorohydride (HArF), was formed by researchers at the University of Helsinki, by shining ultraviolet light onto frozen argon containing a small amount of hydrogen fluoride with caesium iodide.
This discovery caused the recognition that argon could form weakly bound compounds, even though it was not the first.
It is stable up to 17 kelvin s (−256 °C).
The metastable ArCF²⁺
₂ dication, which is valence-isoelectronic with carbonyl fluoride and phosgene, was observed in 2010.
Argon-36, in the form of argon hydride (argonium) ions, has been detected in interstellar medium associated with the Crab Nebula supernova; this was the first noble-gas molecule detected in outer space.

Solid argon hydride (Ar(H₂)₂) has the same crystal structure as the MgZn₂ Laves phase.
It forms at pressures between 4.3 and 220 GPa, though Raman measurements suggest that the H₂ molecules in Ar(H₂)₂ dissociate above 175 GPa.
Argon's complete octet of electrons indicates full s and p subshells. This full valence shell makes argon very stable and extremely resistant to bonding with other elements. Before 1962, argon and the other noble gases were considered to be chemically inert and unable to form compounds; however, compounds of the heavier noble gases have since been synthesized. The first argon compound with tungsten pentacarbonyl, W(CO)₅Ar, was isolated in 1975. However it was not widely recognised at that time. In August 2000, another argon compound, argon fluorohydride (HArF), was formed by researchers at the University of Helsinki, by shining ultraviolet light onto frozen argon containing a small amount of hydrogen fluoride with caesium iodide. This discovery caused the recognition that argon could form weakly bound compounds, even though it was not the first. It is stable up to 17 kelvin s (−256 °C). The metastable ArCF²⁺
₂ dication, which is valence-isoelectronic with carbonyl fluoride and phosgene, was observed in 2010. Argon-36, in the form of argon hydride (argonium) ions, has been detected in interstellar medium associated with the Crab Nebula supernova; this was the first noble-gas molecule detected in outer space.
Solid argon hydride (Ar(H₂)₂) has the same crystal structure as the MgZn₂ Laves phase. It forms at pressures between 4.3 and 220 GPa, though Raman measurements suggest that the H₂ molecules in Ar(H₂)₂ dissociate above 175 GPa.
Argon