Gas molecules have more freedom in motion—and gases can be thought of as more “disordered”—than molecules of a solid, which are rigidly held in place. When it comes to phases, the entropy increases as you go from a solid to liquid to gas (the gaseous state having the greatest entropy and the solid state having the least).
So, as a sample of solid iodine sublimes to form gaseous iodine, the entropy of the sample increases.
