Ionic crystals

• Ionic compounds are formed when metals transfer electrons to non-metals to form ions and they are arranged in a giant 3D lattice where each ion is surrounded by as many oppositely charged ions as possible
• The forces inside the crystal lattice are strong electrostatic forces of attraction between positively charged ions and negatively charged ions and repulsion between ions with the same charge
• Crystalline solids with a high melting/boiling point- strong electrostatic forces of attraction between oppositely charged ions which requires lots of energy to break
• Conduct electricity when molten/in aqueous solution- ions are free to move and carry an electrical charge when they are molten/in solution. As a solid the ions are unable to move and carry an electrical charge.
• Soluble (generally) in polar solvents such as water- the electrostatic forces of attraction between polar water molecules and ions from the ionic lattice are greater than the electrostatic forces of attraction between oppositely charged ions in the lattice.
• A unit cell is the simplest or smallest part of a crystal which when repeated generates the whole crystal.
• The coordination number is the number of nearest neighbours that a given particle is in contact with in a crystalline solid.
• The coordination number for sodium chloride is 6;6
• The coordination number for caesium chloride is 8;8
• Cs+ is larger than Na+ so more Cl- fit around it hence a coordination number of 8.
• Lattice energy is the amount of energy released when the lattice is formed.
• The lattice energy and attractive force increases with: increasing charge on the ions and decreasing size of the ions