What are the differences in boiling points among halogens?

Boiling points increase down the halogen group, from fluorine to iodine, due to increasing molecular size and van der Waals forces.

In the halogen group, which includes fluorine, chlorine, bromine, iodine, and astatine, the boiling points increase as you move down the group. This is due to the increase in the size of the molecules and the strength of the van der Waals forces between them.

Fluorine, being the smallest halogen, has the lowest boiling point at -188.11°C. This is because it has the fewest electrons and therefore the weakest van der Waals forces. As we move down the group, the number of electrons in each halogen increases, leading to stronger van der Waals forces and higher boiling points. Chlorine has a boiling point of -34.04°C, bromine boils at 58.8°C, and iodine has a boiling point of 184.3°C.

Van der Waals forces are temporary, weak forces of attraction that occur between molecules. They are caused by fluctuations in the electron distribution within a molecule, which create temporary positive and negative charges. These temporary charges induce a similar charge in nearby molecules, leading to a weak force of attraction. The more electrons a molecule has, the stronger these forces can be, hence larger molecules with more electrons have higher boiling points.

In summary, the boiling points of the halogens increase from fluorine to iodine due to an increase in molecular size and the strength of the van der Waals forces. This is a key concept in understanding the properties of the halogens and other elements in the periodic table.