Study Notes
Chemical bonding involves the interaction of atomic orbitals to form molecular orbitals, resulting in different types of bonds and molecular structures. Hybridisation explains how atoms like carbon form bonds that are equal in energy.
- Covalent Bonding — A bond formed when two nonmetals share electrons. Example: Hydrogen atoms form a covalent bond by sharing electrons.
- Sigma (σ) Bonds — Formed by the head-on overlap of atomic orbitals. Example: The bond between two hydrogen atoms.
- Pi (π) Bonds — Formed by the sideways overlap of p orbitals. Example: The double bond in ethene consists of one σ and one π bond.
- Hybridisation — The mixing of atomic orbitals to form new hybrid orbitals. Example: Carbon in methane undergoes sp3 hybridisation.
- Octet Rule — Atoms tend to have eight electrons in their valence shell. Example: Neon naturally has a full octet.
- Formal Charge — A method to determine the most stable Lewis structure. Example: Calculating formal charge for CCl4 shows zero charge on each atom.
Exam Tips
Key Definitions to Remember
- Covalent Bonding
- Sigma (σ) Bonds
- Pi (π) Bonds
- Hybridisation
- Octet Rule
- Formal Charge
Common Confusions
- Difference between sigma and pi bonds
- Hybridisation types: sp3, sp2, sp
- Octet rule exceptions
Typical Exam Questions
- What is a sigma bond? A sigma bond is formed by the head-on overlap of atomic orbitals.
- How does hybridisation explain carbon's bonding? Hybridisation explains carbon's ability to form four equal bonds by mixing its orbitals.
- What is the formal charge of an atom? Formal charge is calculated as the number of valence electrons minus half the bonding electrons minus non-bonding electrons.
What Examiners Usually Test
- Understanding of molecular geometry and domain geometry
- Ability to predict bond types and molecular shapes
- Application of formal charge to determine stable structures