Group 17 Elements

F, Cl, Br, I and At constitute the VII A group in periodic table. They are p - block elements and their outer shell configuration is ns2np5.

F2, Cl2, Br2, I2 are known as halogens. Halogen means "Produced in the form of sea salt".

Density, mp, bp, bond length, vander Waal’s forces of attractions and intensity of the colour of the halogens increase down the group.

F2, Cl2 are gases. Br2 is liquid. I2 is solid. The change in physical state is due to the increase in the vander Waal’s force between the molecules down the group which is due to increase in molecular weight.

The order of EA is Cl > F > Br > I. The low EA value of F is due to interelectronic repulsions and due to the small size of F atom. The incoming electron experience greater repulsions due to high electron density in 2 p sub level.