Question

Why does the state of agglomeration (the tendency of molecules to come closer) increase on moving down the group 17?

Answer 1

1. All halogens exist as diatomic molecules with van der Waals forces between molecules.
2. As we move down group 17, atomic size increases due to more electron shells.
3. Larger atoms have stronger van der Waals forces between molecules.
4. Stronger van der Waals forces cause molecules to come closer, increasing agglomeration.
5. This increase in agglomeration leads to a change in physical state from gas (F, Cl) to liquid (Br) to solid (I).

Hence, the state of agglomeration increases down the group due to stronger intermolecular forces with larger atomic size.