1 General properties

3.1.3 Halogens 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 induced dipole-dipole forces (London forces) between the molecules. As the intermolecular forces get larger more energy has to be put into break theses intemolecular forces. This increases the melting and boiling points All halogens exist as diatomic molecules Redox reactions and reactivity of halogens and their compounds Electronic configuration. All group 7 elements have the outer shell s2p 5 electron configuration. The will often react by gaining of one electron in redox reactions to form 1– ions