The gases that has the most similar properties is
Neon (Ne) and Argon (Ar)
Step-by-step explanation
From periodic table both Argon (Ar) and Neon(Ne) are element in group 18 which are referred to as noble gases.
Noble gases are inert since they have eight (8) valence electrons ( electrons in their outermost shell) which make them stable( neither gain or lose electrons)