Ionic Bonding

Calcium reacts with chlorine gas to form calcium chloride.

Identify the type of bonding in calcium chloride, explain how it is formed in terms of electrons and deduce its chemical formula.

[6 marks]

Visual Mark Scheme Breakdown

• What kind of bonding is happening here? (1 mark)

  Looking at the periodic table:

  • Calcium is a metal

  • Chlorine is a non-metal

  Metal + Non-metal = Ionic Bonding

  (1 mark)

• How many electrons do calcium and chlorine have in the outer shell?

  • Calcium is in group 2. So 2 electrons in the outer shell.

  • Chlorine is in group 7. So 7 electrons in the outer shell.

• How are electrons transferred? What ratio of atoms is needed? (3 marks)

  To achieve full outer shell (8 electrons):

  • Ca loses the 2 electrons.

  • Cl gains 1 electron.

  • We need 2 Cl atoms for 1 Ca atom.

    (3 marks)

• What ions are formed? (1 mark)

  • Losing 2 negative electrons means calcium becomes Ca 2+ ion.

  • Gaining 1 negative electron means each chlorine becomes Cl - ion.

  (1 mark)

• What's the formula of the compound? (1 mark)

  One calcium needs two chlorines, so:

  CaCl2

  (1 mark)