Why iodine is solid and fluorine is gas at room temperature?

Answer 1

Iodine is a solid because it has a larger mass number than fluorine. (Iodine=126.9 where as fluoine=19). This means that it will have more induced dipole-induced dipole attractions, compared to flourine. So more attractions need to be overcome in iodine than flourine, meaning there needs to be more energy to overcome the attractive forces. So there will be enough energy at room temperature to overcome the forces of attraction between flourine, making it a gas in nature. However there is not enough energy at room temperature to overcome the attractive forces between iodine, making it a solid at room temperature.

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Answer 2

Iodine is a solid at room temperature because iodine molecules are held together by relatively strong van der Waals forces, which require more energy to break and transition to a liquid or gas. Fluorine is a gas at room temperature as the fluorine molecules are very small and exhibit weak van der Waals forces, allowing them to move more freely and exist in the gaseous state at room temperature.