Chemistry 5.1

• Metals contain many properties like high melting and boiling points, conductors of heat and electricity, and are malleable and ductile along with many more
• Metallic bonding


  Metals are formed in structures as the same element, with their outermost electrons not given to another element but free to move around the structure
• Delocalised electrons with the positive ions form a strong bond as they are arranged in a regular shape
• Metals


  • Conduct heat through vibrations and the sea of electrons
  • Conduct electricity as their free electrons move from negative to positive
• Metals


  • Have high melting and boiling points due to the strong hold the ions and electrons have
  • Are malleable as the layers are made up of atoms that can slide over each other easily while keeping their overall shape
• Ionic bonding


  Ionic compounds contain many properties such as high melting/boiling points, decent conductivity when in a liquid state, and brittleness
• Forming ionic compounds


  1. Metal loses electrons, causing a positive charge

  2. Non-metal gains electrons, causing a negative charge

  3. Only the outer shell needs to be drawn

  4. Arrows must be drawn to show electron movement
• Ionic compounds


  • Have high melting/boiling points due to the strong pull between the oppositely charged ions, giving the compound a fixed crystal shape when solid
  • When melted or dissolved, the ionic bond breaks and the electrons are free to move around, causing the compound to conduct electricity
• Covalent bonding


  Simple covalent substances have low melting/boiling points, are normally gases or liquids, are insulators, and are slightly soluble
• Covalent compounds


  • Chlorine (Cl2)
  • Water (H2O)
• All elements only need 1 or 2 electrons to be stable, similar to the full shells of the noble gases
• Covalent bonds


  • Are strong, yet the molecules are free to move around as there is no repeating structure like in metals
  • Only a small amount of heat is needed to separate the molecules, leading to low melting/boiling points
• Metals are unable to bond like non-metals, and vice versa
• Allotropes


  Different structural forms of the same element
• Main carbon allotropes


  • Diamond
  • Graphite
  • Fullerenes
• Diamond


  • High melting/boiling point, strong bonds, insulator, hard
  • Full electron shells, no conduction
• Graphite


  • Layers, conductor, soft, lubricant
• Fullerenes


  • Ball shape, low carbon, conductor, lubricant
• Uses of carbon allotropes

  • Diamond in power tools and drills
  • Graphite in pencils and lubricants
  • Graphene in electronics and aircraft for strength and conductivity
  • Fullerenes to deliver drugs, as lubricants, and as catalysts
• Nanoscience


  Studies particles 1-100 nm in diameter, which have different properties to the same materials on a bulk scale
• Nanoparticle applications


  • Nano-silver in antibacterial products
  • Nano-titanium and nano-zinc oxides in sunscreens to block UV light
  • Nano-titanium and nano-zinc oxides in self-cleaning windows
• The small size and large surface area to volume ratio of nanoparticles can allow them to enter cells and the bloodstream, potentially causing damage to the environment
• Smart materials


  Materials with special reversible properties that react to their surroundings
• Smart material types


  • Thermochromic pigments (change color with temperature)
  • Photochromic pigments (change color with UV exposure)
  • Shape memory alloys (change shape with heat)
  • Hydrogels/polymer gels (absorb/release water with pH or temperature changes)
• Smart material uses


  • Mugs, mood rings, batteries, thermometers
  • Glasses, money authentication
  • Springs, foldable glasses, car equipment
  • Hair gel, diapers, artificial muscles