CHEMICAL BONDING Metallic Bonding

Overview Bonding IonicCovalentMetallic StructureGiant ionic Simple molecular Giant covalent Giant Metallic Example Sodium chloride WaterDiamondIron Bonding and structure explains the properties of a substance!

Think about metals! What are some properties of metals? Shiny surfaces? Can it be bent? Strong materials? Can it stretch? Good electrical conductor? Good heat conductor?

Physical Properties of Metals AppearanceCan have shiny surfaces Physical stateUsually solid DensityUsually high M.P. & B.P.Usually high Ease of shapingMalleable and ductile Heat and electrical conductivity Good Exception??

Metals Have Giant Structures  Atoms are packed closely together in an orderly manner.  "Giant" implies that large but variable numbers of atoms are involved.

Metallic Bonding  Each metal atom gives up its valence electrons to form positive ions.  These electrons no longer belong to any metal atom  they are delocalised.  They move freely in the space between the metal ions.

‘Sea’ of electrons  The number of delocalized electrons depends on the number of metal ions.  It does not mean an excessive number of electrons.

Metallic Bond: The Definition A metallic bond is… the (electrostatic) force of attraction between positively charged metal ions and negatively charged free or mobile(delocalized) electrons.

Physical Properties: Explanation  Solid, high density  Metal ions are packed tightly in layers.  High M.P. and B.P.  Metal ions and electrons are held together by strong metallic bonds.  Application? Exception? metal ion free electron

Physical Properties: Explanation  Malleable and ductile  When a force is applied to a metal, the layers of atoms can slide over each other easily.  The ‘sea’ of electrons holds the atoms together so that it does not break.

Physical Properties: Explanation  Good electrical conductor  Metals conduct electricity when solid and when molten.  Due to the movement of the delocalized electrons.  Application?

Physical Properties: Explanation  Good heat conductor  Due to the movement of delocalized electrons  When heated, the delocalized electrons gain more energy and move faster, colliding with neighbouring electrons. Heat is transferred in these collisions.  Application?

Ask yourself! 1. List the physical properties of metals. 2. Explain why metals can be malleable or ductile 3. Explain how a metal conduct electricity

So, what have you learnt?  The structure of a metal  a lattice of postive ions in a ‘sea of electrons’  Metallic bonding: the electrostatic force of attraction between positive metal ions and negative electrons.  Physical properties of metals and their explanation