Answer:
six noble gases
Here are five of the six noble gases: helium, neon, argon, kypton and xeon. They're all colourless and transparent. Krypton and xeon form compounds only with difficulty. Helium, neon and argon don't form compounds at all.
There are in total 6 noble gases in the periodic table.
Namely,
1. Helium
2. Neon
3. Argon
4. Krypton
5. Xenon
6. Radon
