CHEMICAL BONDING

Chemical bond: The force of attraction between two particles.

Types of Bonds:

  • Ionic Bond
  • Covalent Bond
  • Metallic Bond

[a] Ionic Bonding

  • Involves the attraction between oppositely charged ions.
  • An atom loses electrons to become positively charged (cation) and gains electrons to become negatively charged (anion).
  • Ionic bonding typically occurs between a metal and a non-metal.

Examples:

  • Na + Cl form NaCl
  • MgCl₂
  • CaO

Structure of Sodium Chloride (NaCl):

  • Sodium and chloride ions are present in equal proportions.
  • The bond is ionic.
  • Ions arrange themselves into a rigid, solid shape known as a crystal lattice.
  • Each Na⁺ ion is surrounded by 6 equidistant Cl⁻ ions, forming a cubic crystal structure, known as a giant ionic structure.

[b] Covalent Bonding

  • Involves the sharing of electrons between atoms.
  • Typically occurs between non-metals.
  • Two or more electrons are shared to form molecules.

Examples:

  • Hydrogen molecule (H₂)
  • Chlorine molecule (Cl₂)
  • Ammonia (NH₃)
  • Water (H₂O)
  • Carbon dioxide (CO₂)
  • Nitrogen molecule (N₂)
  • Oxygen molecule (O₂)
  • Methane (CH₄)

[c] Metallic Bonding

What It Is: Metallic bonding occurs in metals due to a "sea of free electrons."

How It Works:

  • Metals lose outer electrons, forming positive ions.
  • These positive ions are surrounded by delocalized (free-moving) electrons.
  • The strong attraction between the ions and electrons creates a metallic bond.

Properties of Metals:

  • Good Conductors: Free electrons allow electricity and heat to flow easily.
  • Strength: Metallic bond strength increases across a period in the periodic table.

This explains why metals are shiny, malleable, and great conductors!

Activities

  1. Describe bonding in metals.
  2. Below are the electron arrangements for Al and Cu:
    • Al: 2.8.3
    • Cu: 2.8.18.1

    Which element is a better conductor of electricity and heat? Explain.

  3. Using dots and crosses, show the bonding in a water molecule and ammonia.
  4. Two elements, A and B (atomic numbers 6 and 8), react to form C:
    • (a) What is the formula of C in terms of A and B?
    • (b) Show the bonding in C using dots and crosses.
  5. Explain why and how the following conduct electricity:
    • (a) Cu
    • (b) Al
  1. Show the bonding of:
    • Carbon dioxide (CO₂)
    • Carbon monoxide (CO)
    • Methane (CH₄)
  2. Define a chemical bond.
  3. What is the difference between ionic and covalent bonding?
  4. Explain why KCl is unreactive, considering K is very reactive, and Cl is a reactive non-metal.
  5. Write the chemical formulae for the following:
    • Potassium chloride
    • Calcium fluoride
    • Iron (III) oxide
    • Water
    • Aluminium oxide
    • Calcium bromide
    • Sodium oxide
    • Carbon monoxide
  1. Show the bonding of silane (SiH₄)