1.4.9Physical Chemistry
Properties of Metallic Substances — AQA AS Chemistry Revision Notes & Topical Questions
5 min read 4 parts Lesson 25 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.
Section 1 of 4Conduction
Electrical conduction
- Electrical conduction Delocalised electrons are free to move through the lattice, so a potential difference makes them flow as an electric current.
Both states
- Both states Metals conduct as solids and as liquids, because the delocalised electrons remain free whether or not the lattice is fixed.
Thermal conduction
- Thermal conduction Delocalised electrons pass kinetic energy through the metal quickly, and vibrating ions also pass energy to neighbouring ions.
Strength of effect
- Strength of effect Metals with more delocalised electrons per atom usually conduct better, as there are more charge carriers available to move.
Section 2 of 4Shaping and Strength
Shaping and Strength
Malleable
- Malleable Layers of ions can slide over one another when force is applied,
- and the electron sea keeps the structure bonded,
- so metals can be hammered into shapes.
Ductile
- Ductile For the same reason metals can be drawn into wires without breaking, as the ions slide but do not suffer repulsion.
High melting point
- High melting point Strong attraction between positive ions and delocalised electrons means much energy is needed to separate the lattice.
Insoluble
- Insoluble Metals are not dissolved by water or other solvents, since the strong metallic bonding is not overcome by solvent interactions.
| Metal | Delocalised electrons per atom | Relative melting point |
|---|---|---|
| Sodium | 1 | Low |
| Magnesium | 2 | Higher |
| Aluminium | 3 | Higher still |
Section 3 of 4Why Different Metals Differ
1
Compare the charge on the metal ions, since a higher charge attracts the electron sea more strongly.
2
Compare the number of delocalised electrons per atom, which usually increases with the number of outer electrons.
3
Compare the ionic radius, because smaller ions allow the electrons to be nearer to the positive charge.
4
Combine these points to explain trends such as increasing melting point from sodium to aluminium.
5
Be aware that some transition metals show exceptions because their bonding involves more than the outer shell.
Section 4 of 4Exam Checklist & Tips
1.4.9 – Key Points for the Exam
- Malleable Able to be hammered or pressed into shape without breaking.
- Ductile Able to be drawn out into a wire.
- Delocalised electrons Outer electrons that move freely throughout a metallic lattice.
- Thermal conductor A material that transfers heat energy easily.
Common Mistakes
- Saying the metal ions move to carry current; it is the delocalised electrons that move.
- Explaining malleability without saying that the layers slide and bonding is maintained.
- Stating that metals conduct only when molten, instead of in both solid and liquid states.
- Writing that metallic bonding is a bond between two metal atoms rather than a lattice-wide attraction.
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