Question

Why do melting and boiling points of halogens increase on moving down the group?

Answer 1

1. Halogens are made up of diatomic molecules held by weak van der Waals forces.
2. As we move down the group, the size of halogen atoms increases.
3. Larger atoms have stronger van der Waals forces between their molecules.
4. Stronger forces require more energy to break, so melting and boiling points increase.

Thus, fluorine and chlorine are gases, bromine is liquid, and iodine is solid at room temperature.