Lecture Notes: Ionic Bonds and Dot and Cross Diagrams

Introduction to Ionic Bonds

Definition of Ions: Ions are formed when atoms lose or gain electrons.
- Example: Sodium atom losing an electron forms a sodium ion (Na⁺) plus one electron.
- Sodium has one electron in its outer shell, which it needs to lose for stability.
- Chlorine gains an electron to fill its outer shell, forming a chloride ion (Cl⁻).

Electron Transfer: Electrons are transferred from atoms with excess electrons (e.g., sodium) to atoms needing electrons (e.g., chlorine).
- This transfer results in ions with full outer electron shells.
- Ions are shown with square brackets and their charge indicated at the top right.
Electrostatic Attraction: Ionic bonds are formed due to the attraction between oppositely charged ions.
- Ionic bonds are strong and comparable in strength to covalent bonds.

Purpose: These diagrams visually represent the ionic compound formation process.
- Depiction: Electrons from different atoms are represented by dots and crosses.
- Movement of Electrons: Indicated with arrows to show transfer.
- Shells Representation: All shells or just outer shells can be shown, depending on the requirement.

Reactants: Magnesium (Mg) and Chlorine (Cl).
- Magnesium has two electrons in its outer shell to lose.
- Each chlorine atom needs one additional electron.
Electron Movement:
- Magnesium gives one electron to each chlorine atom.
- Results in a magnesium ion (Mg²⁺) and two chloride ions (2 Cl⁻).
Arrangement in Diagram:
- Ions are arranged to reflect real compound structures.
- Chloride ions are positioned on either side of the magnesium ion.

Summary: Understanding ionic bonds involves recognizing electron transfer and electrostatic forces.
Application: Familiarity with drawing dot and cross diagrams is vital for exams.

Closing Note: Practice drawing these diagrams for a better understanding of ionic bonds.