chemical bonding

1. Why Do Atoms Bond?

• Atoms bond to achieve stable electron arrangements, usually by filling their outer electron shells.

• The Octet Rule: Atoms aim for 8 electrons in their outer shell (except for hydrogen and helium, which aim for 2).

2. Types of Chemical Bonds

1. Ionic Bonding:

   • Occurs between metals and non-metals.

   • Metals lose electrons to form positive ions (cations).

   • Non-metals gain electrons to form negative ions (anions).

   • Opposite charges attract, creating a strong bond.

   • Example: Sodium chloride (NaCl).

2. Covalent Bonding:

   • Occurs between non-metal atoms.

   • Atoms share pairs of electrons to achieve full outer shells.

   • Can form single, double, or triple bonds depending on the number of shared electron pairs.

   • Example: Water (H₂O) or oxygen gas (O₂).

3. Metallic Bonding (optional, depending on curriculum):

   • Occurs between metal atoms.

   • Atoms share a "sea of electrons" that move freely.

   • Explains properties like electrical conductivity and malleability.

3. Diagrams to Represent Bonds

• Dot-and-Cross Diagrams:

  • Show electrons from different atoms with dots and crosses.

  • Useful for visualizing how ionic and covalent bonds form.

• Lewis Structures (optional):

  • Represent covalent bonds as lines for shared electron pairs.

4. Properties of Substances Based on Bonding

1. Ionic Compounds:

   • High melting and boiling points.

   • Conduct electricity when molten or dissolved in water.

   • Often form crystalline solids.

2. Covalent Compounds:

   • Low melting and boiling points (for small molecules).

   • Do not conduct electricity (no free ions or electrons).

   • Can form simple molecules or giant structures (e.g., diamond, graphite).

3. Metallic Compounds:

   • High melting and boiling points.

   • Conduct electricity and heat.

   • Malleable and ductile.

5. Key Vocabulary

• Ion: Charged particle formed when atoms gain or lose electrons.

• Molecule: Group of atoms bonded covalently.

• Electrostatic Attraction: The force that holds ions together in ionic bonds.

• Lattice Structure: Regular arrangement of ions in ionic compounds.

• Delocalized Electrons: Electrons in a metallic bond that move freely.

6. Real-Life Examples

• Ionic Compounds: Salt (NaCl), baking soda (NaHCO₃).

• Covalent Compounds: Water (H₂O), carbon dioxide (CO₂), methane (CH₄).

• Metallic Compounds: Copper (Cu) wires, aluminum (Al) foil