Halogens

Question 1

Trend in electronegativity

Answer 1

The electronegativity of the halogens decreases down the group as the radius of each atom increases due to more shells. This means there is less attraction between the positive nucleus and the outer electrons as you go down the group.

Question 2

Trend in reactivity

Answer 2

The group 7 elements need to gain an electron. As atomic radius increases this becomes harder as the positive attraction of the nucleus is weakened by additional shielding. Therefore it is harder to attract an electron so reactivity decreases down the group.

Question 3

Trend in boiling point

Answer 3

The group 7 elements are simple covalent molecules held together with van der waals forces. The strength of these intermolecular forces increases as the Ar of the molecule increases. Therefore the strength of the van der waals forces increases down the group meaning more energy is required to overcome them, resulting in a higher boiling point.
Fluorine is a gas at room temperature whereas iodine is a solid.