Group 7 – the halogens

• The non-metal elements in Group 7 of the periodic table are called the halogens
• They have 7 electrons in their outer shell
• They form 1- ions when they react with metals, producing an ionic compound eg NaCl
• As elements, they exist as diatomic molecules, bonded in pairs eg Cl2, Br2, F2. They share electrons and form a covalent bond
• The reactivity of the halogens decreases as you go down group 7 eg fluorine is more reactive than astatine
• A more reactive halogen can displace a less reactive halogen from a solution of one of its salts
• The halogens have low melting and boiling points, but these increase as you go down the group
• The halogens are poor conductors of heat and electricity
• Melting/boiling points

  A) -220

  B) -101

  C) -7

  D) 114

  E) -188

  F) -35

  G) 59

  H) 184

  
• Halogen displacement reactions with halogen salt solutions

  A) No visible reaction

  B) No visible reaction

  C) Solution darkens

  D) Solution darkens

  E) Solution darkens

  F) No visible reaction

  G) 2

  H) 1

  I) 0