Metallic Bonding

What are the general properties of metals?

How can we explain these 2 properties?

What about flexibility

 

  • Very rare to find real metal-to-metal chemical bonds
  • Even more rare is metal-to-metal with no non-metallic element involved
  • Some metals have a metal as part of a negative ion.

Eg             potassium dichromate (VI) K2Cr2O7

            Potassium manganate (VII) KmnO4

  • Recently caesium auride (CsAu) has been made but this is rare.

 

Metals can form alloys when the atomic radii are close. This can affect their properties. BUT because they do not have a set composition by mass.

 

What are the general properties of metals?

 They all:

    • Conduct electricity
    • Can be bent/rolled into sheets/shaped without breaking/drawn into chains

 BUT, they can have highly variable melting points, (from -39°C (mercury) to 3410°C (tungsten).

 

How can we explain these 2 properties?

 The sea of electron model, helps. Metal atoms exist on a lattice of metal ions (which have lost their outer electrons only temporarily). The lack of fixed position of the e- means they are delocalised.

The electrons are loose, and they all repel

This can help explain how they conduct electricity

What about flexibility?

 

1.                  The positive ions repel as do the negative.

2.                  Strong attraction between positive and the electrons.

 

  • The electrons move constantly, but some electrons will always be between the layers creating an attraction and keeping them attracted to one another.
  • So an impact will allow a shearing effect as there is a degree of repulsion between layers
  • The sea of electrons allows movement of ions, therefore pure metals are not brittle!
  • In a crystal, repulsion from opposite charges causes it to be brittle.