During an experiment, solid iodine was placed in a sealed container. the container was gradually heated and purple-colored vapors of iodine formed were observed. describe this system when it reaches phase equilibrium.

The answer is b electromagnetic i believe, i hope i ya out!

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So the main goal for the elements is stability which is a complete/full valence shell and typically the magic number for a stable element is 8 valence electron but not always. so elements to the left of the periodic table tend to be way less stable then those on the right, so the elements on the left are much more reactive.