Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

1.3.3Physical Chemistry

Metallic Bonding

5 min read 5 parts Lesson 16 of 63

0%read

Section 1 of 5Structure

1.3.3 Metallic Bonding
Lattice
  • Metal atoms are arranged in a regular lattice of positive ions.
Delocalised electrons
  • Outer-shell electrons are released from each atom and move freely throughout the whole structure.
The bond
  • Metallic bonding is the strong electrostatic attraction between the positive metal ions and the sea of delocalised electrons.
Electrons per atom
  • Magnesium has two delocalised electrons per atom whereas sodium has one.

Section 2 of 5Factors Affecting Strength

Factors Affecting Strength
Ionic charge
  • A higher charge on the metal ion gives stronger attraction to the electrons.
Number of electrons
  • More delocalised electrons per atom increase the strength of the bonding.
Ionic radius
  • A smaller ion has a higher charge density and so attracts the delocalised electrons more strongly.
Comparison
  • Mg has a higher melting point than Na as its ions have a 2+ charge, are smaller and release two electrons.

Section 3 of 5Explaining Properties

Electrical conductivity
  • Delocalised electrons can move through the metal when a potential difference is applied.
Malleable and ductile
  • Layers of ions slide over each other without breaking the bonding because the electron sea keeps holding them together.
High melting point
  • A large amount of energy is needed to overcome the strong attraction between ions and delocalised electrons.
Thermal conduction
  • Mobile electrons and vibrating ions pass kinetic energy through the structure quickly.

Section 4 of 5Comparing Metals

Use a clear sequence when asked to explain a difference in melting point between two metals.

1
State the number of delocalised electrons each metal atom contributes to the sea of electrons.
2
Compare the charges on the metal ions, since a higher charge attracts the electron sea more strongly.
3
Compare the ionic radii, remembering that a smaller ion has its charge concentrated over a smaller volume.
4
Conclude that the metal with the stronger metallic bonding needs more energy to separate its ions, so it melts at a higher temperature.
5
For period 3, melting point increases from sodium to aluminium because charge rises from 1+ to 3+ while radius falls.

Section 5 of 5Exam Checklist & Tips

1.3.3 – Key Points for the Exam

  • Metallic bond The electrostatic attraction between positive ions and delocalised electrons.
  • Delocalised electrons Electrons that are not attached to a particular atom and are free to move.
  • Malleable Able to be hammered or bent into shape without breaking.
  • Ductile Able to be drawn into a wire.

Common Mistakes

  • Saying metals contain free atoms or molecules; they contain positive ions in a lattice.
  • Describing the electrons as being between two atoms only, as in covalent bonding.
  • Stating that metals conduct because ions move through the structure.
  • Explaining a difference in melting point without mentioning charge, radius or number of delocalised electrons.
\n