Inert elements of Group 18
Noble gases are six chemical elements in group 18: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). They are characterized by a completely filled outer electron shell, which makes them chemically inert.
Read in glossaryHelium is the second most abundant element in the universe after hydrogen
Each noble gas glows its own color: neon — red, argon — blue
Helium makes voice higher, while xenon makes it lower
Helium was first discovered on the Sun, not on Earth
Xenon is used as a general anesthetic
Noble gases have configuration ns²np⁶ (helium — 1s²). The completely filled outer level makes them very stable and practically unreactive.
Noble gases practically do not undergo chemical reactions. Only xenon and krypton form compounds with fluorine and oxygen under extreme conditions.
| Element | Z | Mass u | M.P. °C | B.P. °C | ρ г/см³ | EN |
|---|---|---|---|---|---|---|
He Helium | 2 | 4.00 ▼ | -272 ▼ | -269 ▼ | 0.00 ▼ | — |
Ne Neon | 10 | 20.18 | -249 | -246 | 0.00 | — |
Ar Argon | 18 | 39.90 | -189 | -186 | 0.00 | — |
Kr Krypton | 36 | 83.80 | -157 | -153 | 0.00 | 3.00 ▲ |
Xe Xenon | 54 | 131.29 | -112 | -108 | 0.01 | 2.60 |
Rn Radon | 86 | 222.00 | -71 | -62 | 0.01 | 2.20 ▼ |
Og Oganesson | 118 | 295.22 ▲ | 52 ▲ | 177 ▲ | 5.00 ▲ | — |
The name 'noble gases' reflects their 'aristocratic' behavior — reluctance to react with other elements. They were formerly called 'inert gases', but after discovery of xenon compounds, the name was changed.
Helium detected in the solar spectrum during an eclipse — first element discovered outside Earth
Rayleigh and Ramsay discovered argon while studying air density
Ramsay and Travers discovered krypton, neon, and xenon within weeks
Neil Bartlett synthesized XePtF₆ — the first xenon compound
Discovered argon, helium on Earth, neon, krypton, and xenon
Created the first noble gas compound (xenon)
Co-discoverer of argon, Nobel Prize in Physics 1904