1 Trends down the group

Fluorine (F2 ): very pale yellow gas. It is highly reactive Chlorine : (Cl2 ) greenish, reactive gas, poisonous in high concentrations Bromine (Br2 ) : red liquid, that gives off dense brown/orange poisonous fumes Iodine (I2 ) : shiny grey solid sublimes to purple gas. Trend in melting point and boiling point Increase down the group As the molecules become larger they have more electrons and so have larger van der waals forces between the molecules. As the intermolecular forces get larger more energy has to be put into break the forces. This increases the melting and boiling points Trend in electronegativity Electronegativity is the relative tendency of an atom in a molecule to attract electrons in a covalent bond to itself. As one goes down the group the electronegativity of the elements decreases. As one goes down the group the atomic radii increases due to the increasing number of shells. The nucleus is therefore less able to attract the bonding pair of electrons