Electrons, Bonding and Structure

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Ionic Bonding and Structure

Ionic Bonding

  • Ionic bonds are present in compounds consisting of a metal and a non-metal. 
  • Electrons are transferred from the metal atom to the non-metal atom.
  • Oppositely charged ions are formed which are bonded together by electrostatic attraction. 

Ionic Structure

  • Each ion attracts oppositely charged ions from all directions.
  • Each ion is surrounded by oppositely charged ions.
  • The ions attract each other, forming a giant ionic lattice.
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Properties of Ionic Compounds

High Melting Point and Boiling Point

  • A large amount of energy is needed to break the strong electrostatic forces that hold the oppositely charged ions together in the solid lattice. 

Electrical Conductivity

  • In a solid lattice the ions are in a fixed position and no ions can move, the ionic compound is a non-conductor of electricity. 
  • When an ionic compound is melted or dissolved in water, the solid lattice breaks down and the ions are free to move. The ionic compound is now a conductor of electricity. 


  • The ionic lattice dissolves in polar solvents, such as water.
  • The polar water molecules break down the lattice by surrounding each ion to form a solution.
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Covalent Bonding and Simple Molecular Structures

Covalent Bonding

  • Covalent bonding occurs in compounds consisting of non-metals.
  • An electron pair occupies the space between the two atoms' nuclei.
  • The negatively charged electrons are attracted to the positive charge of both nuclei.
  • This attraction overcomes the repulsion between the two positively charged nuclei. 
  • Two electrons are shared.
  • In a dative covalent bond, one of the atoms supplies both the shared electrons to the covalent bond. 

Simple Molecular Structures

  • In a solid simple molecular lattice, molecules are held together by weak forces between molecules and the atoms within each molecule are bonded strongly together by covalent bonds. 
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Properties of Simple Molecular Structures

Low Melting and Boiling Point

  • Simple molecular structures have low melting and boiling points because the intermolecular forces are weak van der Waals' forces, so a relatively small amount of energy is needed to break them.

Electrical Conductivity

  • Simple molecular structures are non-conductors of electricity because there are no charged particles free to move. 


  • Simple molecular structures are soluble in non-polar solvents. This is because van der Waals' forces form between the simple molecular structure and the non-polar solvent.
  • The formation of these van der Waals' forces weakens the lattice structure
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Properties of Giant Covalent Structures

High Melting and Boiling Point

  • Giant covalent structures have high melting and boiling points because high temperatures are needed to break the strong covalent bonds in the lattice.

Electrical Conductivity

  • Giant covalent structures are non-conductors of electricity because there are no free charged particles except in graphite.


  • Giant covalent structures are insoluble in both polar and non-polar solvents because the covalent bonds in the lattice are too strong to be broken by either polar or non-polar solvents.
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Giant Covalent Structures: Diamond


  • Tetrahedral structure held together by strong covalent bonds throughout lattice.

Electrical Conductivity

  • Poor conductivity
  • There are no delocalised electrons as all outer-shell electrons are used for covalent bonds


  • Hard
  • Tetrahedral shape allows external forces to be spread throughout the lattice
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Giant Covalent Structures: Graphite


  • Strong hexagonal layer structure, but with weak van der Waals' forces between the layers

Electrical Conductivity

  • Good conductivity
  • There are delocalised electrons between layers
  • Electrons are free to move parallel to the layers when a voltage is applied 


  • Soft
  • Bonding within each layer is strong
  • Weak forces between layers allow layer to slide easily
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Metallic Bonding and Structure

Metallic Bonding

  • The atoms in a solid metal are held together by metallic bonding
  • The atoms are ionised
  • Positive ions occupy fixed positions in a lattice
  • The outer-shell electrons are delocalised

Metallic Structure

  • In a giant metallic lattice the delocalised electrons are spread throughout the metallic structure
  • These electrons are able to move within the structure
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Properties of Giant Metallic Lattices

High Melting and Boiling Points

  • The electrons are free to move throughout the structure, but the positive ions remain where they are
  • The attraction between the positive ions and negative delocalised electrons is strong
  • High temperatures are needed to break the metallic bonds and dislodge the ions from their rigid positions within the lattice

Good Electrical Conductivity

  • The delocalised electrons can move freely anywhere within the metallic lattice
  • This allows the metal to conduct electricity, even in the solid state
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