Group 8a (also referred to as group 18) elements on the periodic table share which characteristics?

The group 18 element on the periodic table are share characteristic of been all non reactive

Example of group 18 element are Helium, Neon, Argon among others. This group 18 element are stable in their outermost energy level (they lack valence electrons.) hence they are no reactive. Example Neon has 8 electron in their outermost energy level hence they are stable.