C2 Bonding, Structure, and Properties of Matter

• The particle model doesn’t show any forces between particles. Each particle, irrespective of its element, is represented as a solid sphere. It is good to show both regular and random atom arrangement,
• Liquid to gas

  Evaporation
• Gas to liquid

  Condensation
• Solid to liquid

  Melting
• Liquid to solid

  Freezing
• Solid to gas

  Sublimation
• Gas

  • Assumes the shape and volume of its container
  • Compressible; lots of free space
  • Particles can move freely around each other

  
• Liquid

  • Assumes the shape of it’s container
  • Not compressible; little free space between particles
  • Flows easily; particles can slide or flow past each other

  
• Solid

  • Fixed volume, shape, and particle arrangement
  • Not compressible; little space between particles
  • Rigid; particles vibrate in the same spot

  
• Physical change…

  • Doesn’t change the particles
  • Can be reversed
  • Changes particle arrangement, movement, and energy
• When a substance melts, some intermolecular bonds are broken
• When a substance evaporate, all its intermolecular bonds are broken
• Ions are atoms with a positive or negative charge as a result of losing or gaining electrons
• Metals tend to lose electrons to form cations (positive ion)
• Nonmetals tend to gain electrons to form anions (negative ion)
• Ionic bonding

  • Between metal atoms and non metal atoms
  • The metal atom transfers electrons from its outer shell to the non metal
  • The metal atom becomes a cation
  • The non metal atom becomes an anion
• To predict the formula of ionic compound, use the ‘swap and drop’ method.

  1. Swap the ionic number of the elements (-3, +)
  2. Add it as subscript to the atom
• Giant ionic lattices are formed when ions are held together by strong electrostatic forces. Every ion is surrounded by ions of opposite charges. There is no limit to the number of ions that can be held together.
• Ionic compounds have a high melting and boiling point because a large amount of energy is needed to break the strong bonds between the ions
• Ionic compounds can only conduct electricity when molten or dissolved in water because the ions are free to move so charge carriers can flow
• The empirical formula is the simplest whole number ratio of atoms of each element in a compound.
• 2D models fail to give a full picture of an ionic lattice. The particles are often not drawn to scale
• On compact 3D models of ionic compounds, it is impossible to see the inner layers and 3 remaining sides.
• The ball and stick model shows the whole structure and arrangement of the ionic compound. However in reality there is no space between ions and you don’t see the relative size.
• Covalent bonding

  • Between nonmetal atoms
  • Electrons are shared between atoms so that they have a full outer shell
  • A double covalent bond is when each atom contributes 2 electrons
• Covalent bonds are strong because the positively charged nuclei are strongly attracted to the negatively charged electron of the other atom
• Displayed formulae are the most simple way to portray single and double covalent bonding

  
• Dot and cross diagrams show the outer electrons of each element as either a dot or cross.

  
• Simple covalent molecules can be liquids solids or gases and have relatively low melting and boiling points

  
• Small Molecules…

  • Have low melting and boiling points; their intermolecular forces (NOT COVALENT) only need a small amount of energy to be broken
  • Are insoluble in water
  • Cannot conduct electricity due to having no free electrons
• Polymers are large molecules made up of many monomers joined together by strong repeating covalent bonds in one direction.
• Inter molecular forces get stronger as molecule size increases
• Giant Covalent Structures

  • Thousands of atom joined together by covalent bonds
  • High melting and boiling points
  • Don’t conduct electricity

  
• Graphite

  • Each Carbon atom is joined to three others by single covalent bonds forming hexagonal rings
  • The rings form layers held together by intermolecular forces
  • Has high melting and boiling points
  • Conducts electricity
• Graphite conducts electricity because each atom has one delocalised electron that is free to carry charge
• Graphite is made up of layers of hexagonal rings. Each layer is bonded by intermolecular bonds. These bonds are weak and this allows for the layers of graphite to slide over each other.
• A single layer of graphite is called graphene. It is a good conductor of electricity and has high melting and boiling points like graphite
• A fullerene is a molecule made up of covalently bonded carbon allotropic atoms arranged in a hollow sphere or tube.

  
• Nanotubes can be used to reinforce tennis racquets, create semiconductors, transport drugs into the body and catalyse reactions.

  
• Metallic Bonding

  • Between metal atoms
  • Create giant structures arranged in regular layers
  • Each atom’s outer electrons are delocalised forming cations
  • This creates strong electrostatic attraction between the cations and the sea of electrons