Chem Topic 2

• What is metallic bonding?

  Metallic bonding is the formation of a lattice (grid) of ions surrounded by a sea of delocalised electrons. As the electrons are free to move, metals are good conductors of heat & electricity.
• What is ionic bonding?

  How metals bond to non-metals. Metal atoms donate electrons to non-metals to form ions.
• How can we show ionic bonding?

  Dot and cross diagrams show the electrons on the outer shells. Metals always end up with an empty outer shell, non-metals with 8 electrons.
• What are ionic structures?

  A lattice of repeating units of positive and negative ions.
• What do ionic substances have and how?

  They have high melting/boiling points due to the strong ionic bonds (ions have strong electrostatic forces between them)
• How can ions conduct electricity?

  When molten or dissolved in a solution. This is because the ions are free to move and carry a charge.
• What are positive and negative ions also known as?

  Positive ions are known as cations, and negative ions are known as anions.
• What are covalent bonds?

  How non-metals bond to each other.

  Atoms share electrons to gain full outer shells.

  Every bond consists of a pair of shared electrons
• How can we show covalent bonds?

  Via dot & cross diagrams or the structural formula
• Why do simple covalent bonds have low boiling ponts?

  Due to weak intermolecular forces meaning little energy is needed to overcome them
• What are giant covalent bonds?

  Structures that consist of repeating units of atoms to make giant molecules.
• What do giant covalent bonds have?

  Very high melting points due to the covalent bonds needing to be broken.
• Why is diamond so strong?

  Because of its very strong bonds consisting of carbon.
• What is graphite?

  An allotrope of carbon.

  It consists of layers of carbons with three bonds each in a hexagonal structure.
• What is an allotrope?

  Made out of same atoms but bonded together in a different way
• What are some properties of graphite?

  • Delocalised electrons that form weak bonds between layers
  • Can conduct electricity as electrons can move
  • Layers can slide past each other (good for pencils)
• What are alloys?

  Mixtures of metals: different size atoms disrupt the lattice, so layers cannot slide over each other easily making it strong
• What are fullerenes/nanotubes used for?

  Electronics,composites and medical purposes
• What is a property of fullerenes/nanotubes?

  Strong and conduct electricity due to delocalised electrons