< Why SO2 gas show non ideal behavior at room temperature but H2 shows ideal?

See below.

Explanation:

SO2 is a polar molecule and so there is interaction between molecules of the gas and  the size of the molecule is large compared with hydrogen . These 2 properties makes it show non ideal behaviour. Also hydrogen is not polar so there is little interaction between molecules.

3 hours because it is a decent distance.

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.