All elements in group 0 have full outer shells so they aren't reactive (inert) since they have no need to gain or lose electrons.
Due to them being more or less inert, they are non-flammable and are colourless at room temperature.
They are hard to observe due to their inertness and was discover late.
Scientist discovered them when they realised the density of nitrogen produced from chemical reactions was different from nitrogen from air, so they realised other gases must have been present. Further noble gases were discovered through fractional distillation.
As you go down group 0 the noble gases get denser.
Uses
Argon is used in filament bulbs -> non-flammable so it stops hot filament from burning away.
Helium in airships -> helium is less denser than air so it floats.
Neon in flashing signs -> neon glows when electricity is passed through it.
