The metallic model - IB DP Chemistry- Study Notes - New Syllabus 2025
The metallic model – IB DP Chemistry- Study Notes
IITian Academy excellent Introduction to the Particulate Nature of Matter – Study Notes and effective strategies will help you prepare for your IB DP Chemistry 2025 exam.
- IB DP Chemistry 2025 SL- IB Style Practice Questions with Answer-Topic Wise-Paper 1
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- IB DP Chemistry 2025 HL- IB Style Practice Questions with Answer-Topic Wise-Paper 1
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S2.3.1-2 – Metallic Structures and Metallic Bonding
Metallic Bonding:
- Occurs when delocalized electrons in metal atoms are attracted to the lattice of positive metal ions.
- Delocalized:→ Electrons do not belong to any one metal nucleus but can spread themselves throughout the metal structure.
- Outer shells are easily lost in metallic structures so positive ions are easily formed.
- When the metal atoms are together, the positive ions form a lattice where the electrons can freely move around.
Factors of Metallic Bond Strength:
1. Number of Delocalized Electrons
- High number of delocalized electrons = Smaller cation = Greater metallic bond strength
- Sodium has one delocalized electron
- Magnesium has two delocalized electrons
- The metallic bond in magnesium will be stronger
2. Size of the Cation
- High charge = Greater metallic strength.
- The strength of metallic bonding tends to decrease down a group as cations increase in size.
- Transition metals have very strong metallic bonds due to the large number of electrons that can become delocalized from both the 3d and 4s sublevels.
3. Charge of the Cation
Properties of Metals:
- Metals are good conductors of electricity and heat
- Due to delocalized electrons moving through the metal structure
- This is also because they have the same electron mobility
Malleability:
- Can be shaped under pressure.
- Usually into thin sheets
- This is because the movement of electrons is non-directional.
Ductility:
- To be drawn into threads.
- High melting points because lots of energy is required to break the strong metallic bonds.
- Shiny and lustrous because the delocalized electrons in the metallic structure reflect light.
Melting Points:
- Tend to decrease down a group
- due to the reduced attraction of the delocalized electrons and the positively charged cations.
- The stronger the metallic bond (due to size of cation and charge), the stronger the melting point
Melting Points of Sodium, Magnesium, and Aluminum:
- Increases across the period.
- Decrease in Ionic Radius
- This reduces the distance between the cations and electrons, increasing the electrostatic attraction between them.
- Increase in Ionic Charge
- This increases the strength of the electrostatic attraction between the cations and delocalized electrons
- Greater Number of Delocalized Electrons Per Ion
- Each aluminum atom contributes 3 valence electrons to the sea of electrons.
- sodium atoms have only one valence electron that becomes delocalize