Neon, krypton, and xenon

Krypton, neon, and xenon were discovered as new zero-valent noble gases. The discovery added to the understanding of the newly discovered noble (or inert) gas group which came to include argon and helium.
 William Ramsay and Morris William Travers England 1898 Neon, krypton, and xenon

Krypton, neon, and xenon were discovered as new zero-valent noble gases. The discovery added to the understanding of the newly discovered noble (or inert) gas group which came to include argon and helium.