When hno2 dissociates in water, which atom is dontaing electrons, allowing water to act as a lewis base?

Answer to this is O-atom.

Explanation: The Bronsted acid-base theory is the backbone of chemistry. This theory focuses mainly on acids and bases acting as proton donors or proton acceptors.

where is the Lewis Acid and is the Lewis Base and is the Covalent Bond.

Reaction of dissociation of in is given as:

In this reaction O-atom has lone pair in water and therefore it accepts the proton from forming a Lewis Base.

the volume increases

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).