1.8.1States of Matter
Metallic Bonding — Cambridge IGCSE Chemistry 0620 Revision Notes & Topical Questions
5 min read 4 parts Lesson 19 of 30 Unit quiz
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.
Section 1 of 4The Metallic Bond
The outer electrons of metal atoms are not held by any single atom.
Metal lattice
- Metal lattice A giant regular arrangement of positive metal ions packed in layers, rather than separate molecules.
Delocalised electrons
- Delocalised electrons Outer electrons released by the metal atoms that move freely through the structure instead of belonging to one atom.
Metallic bond
- Metallic bond The strong electrostatic attraction between the positive metal ions and the surrounding delocalised electrons.
Sea of electrons
- Sea of electrons A model in which delocalised electrons move between the positive ions and hold the whole structure together.
Section 2 of 4Properties Explained
Properties Explained
High melting point
- High melting point The strong attraction between ions and electrons needs a large amount of energy to overcome,
- so most metals melt at high temperatures.
Electrical conduction
- Electrical conduction Delocalised electrons move through the structure and carry charge when a potential difference is applied across the metal.
Malleability
- Malleability Layers of ions slide over each other when hammered,
- because the metallic bond is not fixed in one direction,
- so the metal changes shape without breaking.
Thermal conduction
- Thermal conduction Delocalised electrons transfer thermal energy quickly through the metal, which is why metals conduct heat well.
Section 3 of 4Alloys
1
An alloy is a mixture of a metal with another element, usually another metal or carbon, combined to give better properties.
2
Atoms of different sizes in an alloy distort the regular layers of the metal lattice.
3
The distorted layers find it harder to slide over one another, so the alloy is harder and stronger than the pure metal.
4
Alloys often resist corrosion or extreme temperatures better than pure metals, which makes them more useful in practice.
| Alloy | Made from | Typical use |
|---|---|---|
| Mild steel | Iron with about 0.25% carbon | Car body panels and wiring |
| High carbon steel | Iron with 0.5 to 1.4% carbon | Tools such as chisels |
| Brass | Copper with about 30% zinc | Decorative items and fittings |
| Stainless steel | Iron with chromium and nickel | Cutlery, sinks and chemical plant |
Section 4 of 4Exam Checklist & Tips
1.8.1 – Key Points for the Exam
- Metallic bond The electrostatic attraction between positive metal ions and delocalised electrons.
- Delocalised electron An electron that is free to move through the metal lattice.
- Malleable Able to be hammered or pressed into shape without breaking.
- Alloy A mixture of a metal with another element, designed to have improved properties.
- Metal lattice The regular arrangement of positive metal ions in a metal.
Common Mistakes
- Saying the lattice is made of metal atoms; in a metal the lattice is made of positive metal ions.
- Describing the metallic bond as electrons shared between two specific atoms.
- Explaining malleability by bonds breaking; the layers slide while the metallic bonding stays in place.
- Using the word particles when explaining malleability; name the atoms or ions in the layers.
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