they are lighter than air. they have full outer electron shells. they have excess electrons to share. they easily react with other elements.
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: On the periodic table, the elements in group 18 (8A) (helium, neon, argon, etc.) are grouped together because
Possibilities:
- they are lighter than air.
- they have full outer electron shells.
- they have excess electrons to share.
- they easily react with other elements.

they have full outer electron shells.