Topic 2: Bonding, structure and the properties of matter

• Ion

  Electrically charged particle formed when an atom loses or gains electrons
• Atoms

  • Lose electrons to achieve the stable electronic structure of a noble gas (full outer energy level)
  • Gain electrons to achieve the stable electronic structure of a noble gas (full outer energy level)
• Cations

  Positively charged ions
• Anions

  Negatively charged ions
• Ionic bonding

  Relatively strong electrostatic attraction between oppositely charged ions (positive and negative ions)
• Ionic bonding

  Electrons are transferred between atoms of metals and non-metals
• Covalent bond

  Shared pair of electrons between two atoms of non-metals
• Metals

  • Consist of giant structures of atoms arranged in a regular pattern
• Metallic bonding

  Force of attraction between delocalised electrons and positive nuclei of metal ions
• Metallic bonding

  • Electrons in the outer energy level of metal atoms are delocalised and so are free to move through the whole structure of the metal
  • Strong electrostatic attraction between positive metal ions and the delocalised electrons
• States of matter

  • Solid
  • Liquid
  • Gas
• Energy needed to change state

  Depends on the strength of the forces between the particles of the substance
• Particles

  Depend on the type of bonding and the structure of the substance
• Stronger forces between particles

  Higher melting point and boiling point of the substance
• Limitations of the simple model of representing the three states of matter are that forces are not shown, and particles are represented as solid spheres
• Ionic compounds

  • Held in a giant regular lattice structure by strong electrostatic forces that act in all directions in the lattice
  • Solids at room temperature
  • Have high melting and boiling points due to strong electrostatic forces between oppositely charged ions which need a lot of energy to overcome
  • Do not conduct electricity when solid as the ions are in fixed positions and so cannot move
  • Only conduct electricity when molten or dissolved in water as ions separate so are free to move
• Substances containing small molecules

  • Have strong covalent bonds between atoms but weak intermolecular forces between molecules
  • Are gases and liquids at room temperature
  • Have low melting and boiling points due to weak intermolecular forces between molecules which need little energy to overcome
  • Do not conduct electricity as there are no ions so no overall electric charge
• As the mass or size of a molecule increases

  The intermolecular forces increase, so melting and boiling points increase, as more energy is needed to overcome these forces
• Polymers

  • Have very large molecules with the atoms in the polymer molecules linked to other atoms by strong covalent bonds in long chains
  • Are solids at room temperature as there are relatively strong intermolecular forces between polymer molecules
• Giant covalent structures

  • Contain many atoms bonded together in a giant lattice structure by strong covalent bonds
  • Are solids at room temperature
  • Have very high melting and boiling points due to strong covalent bonds between atoms which need a lot of energy to break
• Giant covalent structures

  • Diamond
  • Graphite
  • Silicon dioxide
• Metals

  • Have high melting and boiling points because the strong electrostatic forces between positive metal ions and delocalised electrons needs a lot of energy to overcome
  • Can conduct heat and electricity as delocalised electrons are free to move through the structure of the metal and carry thermal energy and electrical charge
• Alloys

  Mixtures of metals with other elements, usually metals
• Alloys

  • Are harder than pure metals because different sized metal atoms distorts the regular layers, so they cannot slide over each other
• Allotropes of carbon

  • Diamond
  • Graphite
  • Fullerenes
  • Nanotubes
  • Graphene
• Diamond

  • Each carbon atom is bonded to 4 others by strong covalent bonds, making it very hard
  • Has very high melting and boiling points because the strong covalent bonds need a lot of energy to break
  • Does not conduct electricity as it does not have delocalised electrons
• Graphite

  • Each carbon atom is bonded to 3 others by covalent bonds
  • Consists of layers of hexagonal rings, which have no covalent bonds between the layers
  • Has high melting and boiling points because the strong covalent bonds need a lot of energy to break
  • Conducts heat and electricity because one electron from each carbon atom is delocalised
  • Is very soft as layers in graphite can slide over each other due to weak intermolecular forces between layers
• Graphene

  A single layer of graphite
• Graphene

  • Has properties which make it useful in electronics and composites
  • Is very strong as the strong covalent bonds between carbon atoms need a lot of energy to break
• Fullerenes

  Hollow shaped molecules based on hexagonal rings of carbon atoms, but some rings may have five or seven carbon atoms
• Buckminsterfullerene

  • The first fullerene to be discovered
  • Has a spherical shape and simple molecular structure of sixty carbon atoms bonded together by strong covalent bonds
• Buckminsterfullerene

  • Is slippery and has a low melting point as it has weak intermolecular forces between molecules which need little energy to overcome
• Nanotubes

  Cylindrical fullerenes with high length to diameter ratio
• Nanotubes

  • Are strong and have high tensile strength as the strong covalent bonds between carbon atoms need a lot of energy to break
  • Conduct electricity because they have delocalised electrons
  • Have properties which make them useful for nanotechnology, electronics and specialised materials
• Nanoparticles

  • Tiny particles, typically between 1 and 100 nanometres in diameter
  • Contain only a few hundred atoms
• Nanoparticles

  • Have a high surface area to volume ratio, so they have different properties from those for the same materials in bulk
  • Smaller quantities of nanoparticles needed to be effective than for materials with normal particle sizes
• Nanoparticles are used in medicine (drug delivery systems) as tiny particles are more easily absorbed by the body than other particles
• Nanoparticles are used in electronics as some nanoparticles can conduct electricity
• Nanoparticles are used in deodorants as silver nanoparticles have antibacterial properties, can kill bacteria and fungi, and also stop sweating
• Nanoparticles are used in sun creams as it is better skin coverage and more effective protection against cell damage from the sun's UV rays