Which of the following gases diviates from ideal bihaviour?

A)so2

B)ch4

C)h2

D)n2

SO2 has an O single bonded to S and an O double bonded to S. This makes the molecule polar (one side hogs more electrons than the other, creating a significant dipole moment)  

Now, SO2 is the only one of these that is polar. This polarity increases its attraction to other SO2 molecules because the positively charged side of one SO2 is attracted to the negatively charged side of another SO2. Because the molecules are attracted to each other, they are more inclined towards clumping together. Ideal gases are assumed to move freely and have no effects on each other, so clearly SO2 is the least ideal. 
Hence option A is correct.

 

Regards

Arun