Overview
This lecture explains how ionic bonds form between atoms through the transfer of electrons, using dot and cross diagrams to illustrate particle interactions, with examples involving sodium chloride and magnesium chloride.
Ions and Electron Transfer
- Ions form when atoms lose or gain electrons to achieve a full outer electron shell.
- A sodium atom (Na) loses one electron to become a Na⁺ ion.
- A chlorine atom (Cl) gains one electron to become a Cl⁻ ion.
- Electron transfer typically occurs between atoms with too many and too few electrons in their outer shell.
Formation of Ionic Bonds
- Oppositely charged ions are attracted to each other by strong electrostatic forces called ionic bonds.
- Ionic bonds create ionic compounds, which have high bond strength similar to covalent bonds.
Dot and Cross Diagrams
- Dot and cross diagrams visually represent the electrons in ionic bonding.
- Electrons from one atom are drawn as dots, the other's as crosses, to show their origin.
- Arrows indicate the movement of electrons from one atom to another.
- Diagrams can show all electron shells or just the outermost shell for simplicity.
- Ions are shown in square brackets with their charge indicated.
Example: Sodium Chloride (NaCl)
- Sodium donates one electron to chlorine, resulting in Na⁺ and Cl⁻ ions, both with full outer shells.
Example: Magnesium Chloride (MgCl₂)
- Magnesium (Mg) has two outer electrons and two chlorine atoms each need one electron.
- Magnesium donates one electron to each chlorine, forming Mg²⁺ and two Cl⁻ ions.
- In diagrams, arrange chloride ions on either side of the magnesium ion to reflect the compound's structure.
Key Terms & Definitions
- Ion — An atom or group of atoms with a net electric charge due to loss or gain of electrons.
- Ionic Bond — The strong electrostatic attraction between oppositely charged ions.
- Dot and Cross Diagram — A diagram showing the transfer of electrons using dots and crosses to represent different atoms' electrons.
Action Items / Next Steps
- Practice drawing dot and cross diagrams for other ionic compounds, showing only the outermost shells.
- Review ionic bonding concepts for upcoming assessments.