1.2.6 Group 7: The Halogens

• State 5 characteristics of Group 7?

  7 electrons in outer shell, Coloured vapours, Diatomic molecules, Form ionic salts with metals, Form molecular compounds with non-metals.
• State five Group 7 elements and the states of matter of molecules they form.

  Fluorine: F.F>2 is a pale yellow gas, Chlorine: Cl, Cl>2 is a pale green gas, Bromine: Br. Br>2 is a dark brown liquid, Iodine: I. I>2 is a grey solid.
• State three changes that occur in Group 7 as one moves down the Group.

  Higher relative molecular mass, Higher melting and Boiling Point, Less reactive - less easily gain electrons.
• A more reactive halogen displaces a less reactive one from an aqueous solution of its salt; explain the trend in reactivity of halogens in these reactions.

  Reactivity decreases down the group. As we go down the group, the atoms get larger, so an incoming electron will be less tightly held by the attractive forces from the nucleus. That's why Cl>2 displaces Br- and l-.