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Ionic Bonds & Lattice Structure (Cambridge O Level Chemistry)
Revision Note
The Lattice Structure of Ionic Compounds
Lattice structure
- Ionic compounds have a giant lattice structure
- Lattice structure refers to the arrangement of the atoms of a substance in 3D space
- In lattice structures, the atoms are arranged in an ordered and repeating fashion
- The lattices formed by ionic compounds consist of a regular arrangement of alternating positive and negative ions
The lattice structure of NaCl
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Ionic Bonds between Metallic & Non-Metallic Elements
Ionic compounds
- Ionic compounds are formed when metal atoms and non-metal atoms react
- The ionic compound has no overall charge
Example: Magnesium Oxide, MgO
Diagram showing the dot-and-cross diagram of magnesium oxide
Explanation
- Magnesium is a Group II metal so will lose two outer electrons to another atom to have a full outer shell of electrons
- A positive ion with the charge 2+ is formed
- Oxygen is a Group VI non-metal so will need to gain two electrons to have a full outer shell of electrons
- Two electrons will be transferred from the outer shell of the magnesium atom to the outer shell of the oxygen atom
- Oxygen atom will gain two electrons to form a negative ion with charge 2-
- Magnesium oxide has no overall charge
Formula of ionic compound: MgO
Examiner Tip
When drawing dot and cross diagrams, you only need to show the outer shell of electrons. Remember to draw square brackets and include a charge for each ion. Make sure the overall charge is 0; you may need to include more than one positive or negative ion to ensure the positive and negative charges cancel each other out.
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