Bonding and Structure

• What are ions?


  charged particles
• Why do atoms lose or gain electrons?

  To get a full outer shell and become stable
• What ions do metals form?

  positive ions
• What ions do non-metals form?

  negative ions
• What groups form positive ions?

  Group 1 and 2
• What groups form negative ions?

  Groups 6 and 7
• What is ionic bonding?


  The strong attraction of oppositely charged ions by electrostatic forces
• What elements is a ionic bond between?

  Metals and non metals
• What structure do ionic compounds have?

  Giant ionic lattice
• How to show a giant ionic lattice?

  3d model and ball and stick model
• properties of ionic compounds

  Form crystal lattices, conduct electricity in solution, and have high melting and boiling points.
• How to work out the empirical formula


  Work out charges of the ions in the formula and then balance the charges so that the charge of the empirical formula is zero
• Covaelent Bonding


  Bond formed between a non metal and a non metal by electrostatic forces making the bond very strong
• how to draw a covalent bond

  Dot and cross diagram,displayed formula,3d model
• Dot and cross diagram

  -useful as it shows which atoms the electron in covalent bond come from

  -however don't show relative sizes or how atoms are arranged
• Displayed formula


  Shows how atoms are connected in large molecules but doesn't show the 3d structure or which atoms the electrons in the covalent bond come from
• 3d model


  shows atoms, covalent bonds and their arrangement but can be confusing for large molecules or where electrons from bonds have come from
• Examples of simple molecular substances

  Hydrogen(H2),chlorine(Cl2),oxygen(O2),nitrogen(N2),methane(CH4),water(H2O),hydrogen chloride (HCL)
• Which simple molecular substances from single bonds?

  Hydrogen,chlorine,water,hydrogen chloride
• Which simple molecular substance form a double bond?

  Oxygen
• Which simple molecular substance forms a triple bond?

  Nitrogen
• Properties of simple molecular substances

  held together by strong covalent bonds but weak intermolecular forces, very low melting and boiling points and dont conduct electricity
• Polymers


  Lots of small units which are linked together to form a long molecule that has repeating sections
• How to draw a polymer

  repeating unit

  square brackets

  trailing bonds

  n outside the bracket
• Properties of polymers


  Large intermolecular forces, solid at room temperature, lower boiling points
• Giant covalent structure


  Where all the atoms are bounded by strong covalent bonds
• Properties of giant covalent structures

  - Very high melting and boiling points

  - Only graphite conducts electricity
• main examples of giant covalent structures?

  Diamond, graphite, silicon dioxide
• Structure of diamond


  Each carbon atom forms four covalent bonds in a very rigid giant covalent structure
• Structure of graphite


  Each carbon atom forms three covalent bonds to create layers of hexagons. Each carbon atom also has one delocalised electron.
• Structure of silicon dioxide

  each silicon atom is covalently bonded to 4 oxygen atoms and each oxygen atom is covalently bonded with 2 silicon atoms
• Properties of diamond


  Hard

  High melting point

  Does not conduct electricity
• Properties of graphite


  Soft, Slippery, good conductor of heat and electricity and thermal energy
• What is graphene?


  A sheet of carbon atoms joined together in hexagons - it's one atom thick, therefore it's a 2-dimensional compound

  The network of covalent bonds makes it very strong

  Very light - added to composite materials to improve their strength but not to add weight

  Contains delocalised electrons - conducts electricity through the whole structure

  Can be used in electronics
• Fullerenes


  Molecules of carbon shaped like closed tubes or hollow balls
• Properties of fullerenes


  - cage-like structures able to be used in drug delivery (new cancer treatment including radioactive atoms in these)

  - lubricants (such as graphite)

  - Catalysts (large SA to volume ratio of their nanoparticles)
• What can fullerenes form?

  Nanotubes - tiny carbon cylinders
• Example of a fullerene

  Buckminsterfullerene (C60)
• What is a nanotube?


  Tiny carbon cylinders which have a high ratio between the length and diameter,can conduct electricity and thermal energy, have high tensile strength, used in nanotechnology and to strengthen materials or used in electronics
• metallic bonding


  When the electrons in the outer shell of the metal atoms are delocalised, there are strong forces of attraction between the positive metal ions and the shared negative electrons, these forces of attraction hold the atoms together in a regular structure and are known as metallic bonding