What group might group 16 most readily react with?
For the most part, Group 16 forms -2 ions, therefore they most readily bond with Group 2, which primarily form +2 ions.
Vinegar is a solution of a carboxylic acid (acetic acid) which means that most metal compounds (particulaly alkaline metal compounds found in group 1 in the periodic table) will react with it to produce salts, carbon dioxide and water. Sodium Carbonate is a common example of a alkaline metal compound that reacts readily with vinegar.
group 18 elements are what we call noble gasses. This means that their most outer shell called the valence shell has all 8 electrons. The reason why other elements are reactive is because all elements want to have a full valence shell because it makes them more stable. The noble gasses have a full shell so they are not very reactive.
Group 18 is the most stable group (the noble or inert gases) because their electron configuration makes it difficult for them to react with other elements. The outer valence shell is completely filled already, so they don't need to share, give away, or take electrons to fill it (and thus react with something else.)