Ionic Bonding and Structure

Bonding Questions: E.g. melting point question ‘in terms of bonding and structure.’
– Name structure.
– Name bond.
– Write what the attraction is between e.g. + metal ions and –ve delocalised electrons in
metallic, atoms in covalent bond and molecules in simple molecular.
– Also can define if not done already.
• Ionic Bonding: Is the electrostatic attraction between oppositely charged ions.
• When given table and comparing melting points, don’t go too in depth. If numbers are similar,
that’s good enough. If melting point much larger, then state if giant covalent or giant ionic.
• Ions: Common cations are metal ions and ammonium ions. Common anions are non- metal ions
and polyatomic ions. Ions formed have outer shells with same electron configuration as nearest
noble gas.
• Dot and Cross Diagram: Only outer shells shown but for full outer shell leave empty and just draw
a circle. In ionic bonding draw more than one ion if needed, e.g. two magnesium ion for every
oxygen. Don’t draw squiggly line like I did at GCSE. But remember ionic charges.
• Don’t assume covalent when see dot and cross, check periodic table.
• Structure of Giant Ionic Lattice: Each ion is surrounded by oppositely charged ions in the
structure. It is a regular cubic arrangement. Don’t write ionic, write giant ionic.
• High Melting and Boiling Point:
– Ionic compounds need high temperatures to provide larger quantity of energy.
– To overcome strong electrostatic forces of attraction between oppositely charged ions.
• Greater Ionic Charge and Larger Size:
– Lattices have higher melting point
– due to stronger attraction between ions when…
– Smaller ion size.
– Greater ionic charges.
• Soluble: Many ionic compounds dissolve in polar solvents such as water. The ionic lattice breaks
down as water molecules surround the positive and negative ions.
– The positive ion is attracted towards the oxygen of the water molecule as it is δ-.
– The negative ion is attracted towards the hydrogen of the water molecule as it is δ+.
– Lattices with ions with greater ionic charges will be too strong for water to break it down so it
will not be soluble.
• Electrical Conductivity as Solid: Ions are fixed in position in an ionic lattice so are not mobile in a
solid. Cannot conduct electricity.

Electrical Conductivity as Liquid, Molten or Aqueous: Solid ionic lattice breaks down. Ions can
move and conduct electricity when molten, have mobile ions.
NH4Cl an ionic compound