1.4.6Physical Chemistry
Metallic Bonding — AQA AS Chemistry Revision Notes & Topical Questions
5 min read 4 parts Lesson 22 of 102
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 4The Model
Giant lattice
- Giant lattice Metal atoms are packed closely in a regular giant lattice, which is held together by metallic bonding throughout the whole structure.
Positive ions
- Positive ions Each metal atom gives up its outer electrons and becomes a positive ion that stays in a fixed position in the lattice.
Delocalised electrons
- Delocalised electrons The outer electrons are not attached to one atom but move freely through the structure as a sea surrounding the ions.
Metallic bond
- Metallic bond The metallic bond is the electrostatic attraction between the lattice of positive ions and the delocalised electrons.
No directional bonds
- No directional bonds The attraction acts in all directions, so metal ions can change position without breaking the bonding altogether.
Part 2 of 4Factors Affecting Strength
Factors Affecting Strength
Ionic charge
- Ionic charge A higher positive charge on the ion attracts the delocalised electrons more strongly, so the bonding is stronger.
Delocalised electrons
- Delocalised electrons Atoms that release more electrons into the sea create a greater density of negative charge, which strengthens the attraction.
Ionic radius
- Ionic radius Smaller ions bring the positive charge closer to the electron sea, so the electrostatic attraction is greater.
Period 3 trend
- Period 3 trend Sodium, magnesium and aluminium give 1, 2 and 3 delocalised electrons per atom, so metallic bonding strengthens across this series.
| Metal | Ion | Delocalised electrons per atom |
|---|---|---|
| Sodium | Na⁺ | 1 |
| Magnesium | Mg²⁺ | 2 |
| Aluminium | Al³⁺ | 3 |
Part 3 of 4Linking Bonding to Behaviour
1
Start by stating the structure: a lattice of positive ions surrounded by delocalised electrons.
2
Explain that the electrons are free to move, which accounts for electrical conduction in the solid and liquid.
3
Explain that layers of ions can slide over each other while the electron sea keeps them bonded, which allows shaping.
4
Relate melting point to the strength of attraction between ions and electrons, which depends on charge and size.
5
Always refer to ions and electrons, never to molecules, since a metal does not consist of molecules.
Part 4 of 4Exam Checklist & Tips
1.4.6 – Key Points for the Exam
- Metallic bond The electrostatic attraction between positive metal ions and delocalised electrons.
- Delocalised electron An electron that is not bound to one atom but is free to move through the structure.
- Lattice A regular three-dimensional arrangement of particles.
- Cation A positively charged ion, such as the ions in a metal lattice.
Common Mistakes
- Saying metals contain free atoms or molecules; they contain positive ions and delocalised electrons.
- Stating that the electrons are negative ions; electrons are particles, not ions.
- Describing metallic bonding as attraction between the metal atoms rather than between ions and electrons.
- Forgetting that the ions are fixed in place while only the electrons move freely.
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