AQA GCSE FOUNDATION Chemistry: Ionic Bonding and Properties

AQA GCSE Foundation Chemistry: Ionic Bonding and Properties

Introduction

Ionic bonding is a type of chemical bond formed between metals and non-metals. It involves the transfer of electrons from the metal atom to the non-metal atom, forming ions with opposite charges. These oppositely charged ions then attract each other strongly, forming a lattice structure.

Structure

• Formation of Ions:

  • Metal atoms lose electrons to become positively charged ions (cations).
  • Non-metal atoms gain electrons to become negatively charged ions (anions).

• Lattice Structure:

  • The oppositely charged ions arrange themselves in a regular, repeating pattern called a lattice.
  • This structure is held together by strong electrostatic forces of attraction between the positive and negative ions.

• Example: In sodium chloride (NaCl):

  • Sodium (Na) loses an electron to become a sodium ion (Na?).
  • Chlorine (Cl) gains an electron to become a chloride ion (Cl?).
  • These ions arrange themselves in a cubic lattice where each sodium ion is surrounded by six chloride ions, and each chloride ion is surrounded by six sodium ions.

Properties of Ionic Compounds

• High Melting and Boiling Points: The strong electrostatic forces between the ions require a lot of energy to overcome, resulting in high melting and boiling points.
• Solubility in Water: Water is a polar molecule, meaning it has a positive and negative end. These ends can interact with the ions in the ionic compound, breaking the lattice and dissolving the compound.
• Conductivity: Ionic compounds are good conductors of electricity when dissolved in water or melted. This is because the ions are free to move and carry the electric current.
• Brittle: The strong electrostatic forces holding the lattice together make the ionic compound brittle. If a force is applied, the ions are pushed past each other, causing the lattice to break.

Example: Sodium Chloride (NaCl)

• Formation: Sodium (Na), a metal, loses an electron to become a sodium ion (Na?). Chlorine (Cl), a non-metal, gains an electron to become a chloride ion (Cl?).
• Structure: The Na? and Cl? ions form a cubic lattice with strong electrostatic forces holding the ions together.
• Properties: Sodium chloride has a high melting point (801 °C), is soluble in water, conducts electricity when dissolved or molten, and is brittle.

Conclusion

Ionic bonding is a fundamental concept in chemistry, responsible for many of the properties of ionic compounds. Understanding the formation of ionic compounds, their lattice structure, and their properties is crucial for comprehending chemical reactions and the behavior of matter.