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Chapter 3 — chapter 3
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📘Easy summary
A chemical bond forms when the force of attraction between atoms overcomes the force of repulsion, lowering energy. Ionic bond: transfer of electrons from a metal of low ionization energy to a non-metal of high electron affinity (Na⁺Cl⁻). Covalent bond: sharing of electron pairs (single H–H, double O=O, triple N≡N). Coordinate (dative) bond: both shared electrons come from one atom (NH₃→H⁺ in NH₄⁺, H₃O⁺, NH₃→BF₃). Metallic bond: positive kernels in a sea of delocalized electrons. Lewis structures show valence electrons; some molecules have incomplete octets (BF₃) or expanded octets (PCl₅, SF₆, ICl₅, PO₄³⁻) because P, S, Cl, I have empty d-orbitals.
⭐Key points
- Bond: attraction > repulsion.
- Ionic: low IE + high EA.
- Dative: both electrons from one atom.
🔬Diagram
🌿Real-life example
NH₄⁺ has three covalent and one dative N→H bond (all identical).
💡Exam tip
- Show lone pairs in Lewis structures.
✅Quick check
1. Dative bond present in:
2. Ionic A⁺B⁻ forms when:
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