C3

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  • C3-Structure and bonding
    • Ionic bonding
      • Happens between a metal and non-metal
        • Metals form a positive ion whereas non-metals form a negative ion
      • An ion is a charged particle
      • Can be represented through the dot-cross diagram
      • Electrostatic forces of attraction
        • Ions form a closely packed regular lattice arrangement with strong electrostatic forces of attraction between oppositely charged ions, in all directions
          • Cannot conduct electricity and has high boiling points to overcome attractions
            • But in molten or aqueous state they can conduct electricity
              • Easy to dissolve in water
    • States of matter
      • Solids have a fixed shape and volume so they cannot be compressed
        • Liquids have a fixed volume but they can flow and change their shape
        • Gases have no fixed shape or volume and can be compressed easily
      • Limitations of the particle model
        • This simple particle model assumes that particle are made up of solid spheres with no forces between them. However, particles that make up substances are atoms, molecules and ions.
        • They can vary in size and may not be spherical. Interactions from molecules and ions can also distort their shapes. Atoms are mostly empty space so real particles are not solid at all
    • Covalent bonding
      • When non-metals react together they share pairs of electrons to make covalent bonds
      • The positively charged nuclei of the bonded atoms are attracted to the shared pair of electrons by electrostatic forces, making covalent bonds very strong
      • Atoms only share electrons in their outer shells
      • There are 2 ways of showing covalent bonds
    • Giant covalent structures
      • Polymers
        • Polymers are long chains of repeating units
        • In a polymer, lots of small units are linked together to form a long molecule that has repeating sections which are joined by strong covalent bonds
        • The inter-molecular forces between polymer molecules are larger than between simple covalent molecules so more energy is needed to break them
        • They are solids at room temperature
      • In giant covalent structures, all the atoms are bonded to each other by strong covalent bonds. They have very high boiling and melting points
        • Diamond (carbon)
          • Each carbon atom forms four covalent bonds. This makes diamond really hard and why it is used for rings.
            • These 4 covalent bonds require a lot of energy to break so it has a very high melting point
              • It doesn't conduct electricity because it has no free electrons
          • Carbon can only make 4 bonds because it has 4 electrons on its valence shell
      • Graphite
        • Each carbon atom forms three covalent bonds to create layers of hexagons. Each carbon atom has 1 delocalised electron.
          • There are no covalent bonds between the layers. They're only held together weakly which makes graphite slippery and a lubricant
          • Graphite has a high melting point and can conduct electricity because of the delocalised electron
        • Graphene
          • Graphene is a sheet of carbon atoms joined in hexagons
            • It is only one atom thick
              • It is strong but light so it can be added to other materials without putting lots of weight on it and it CAN conduct electricity
      • Silicon dioxide
        • Sometimes called silica, this is what sand is made of
        • Each grain of sand is one giant structure of silicon and oxygen
      • Fullerenes
        • Fullerenes are molecules of carbon shaped like closed tubes or hollow balls
          • They're mainly made out of carbon arranged into hexagons and can also contain pentagons or heptagons
          • They have huge surface areas which make them great catalysts and lubricants
          • Fullerenes can form nanotubes-tiny carbon cylinders which can conduct electricity and thermal energy and can strengethen objects (similar to graphite)
    • Simple molecular forces
      • Need to know 7: H2, O2, CH4, Cl2, N2, H20, HCL
        • The atoms within molecules  are held together by very strong covalent bonds but forces between the molecules are very weak
          • They don't conduct electricity and the melting points are very low
    • Metallic bonding
      • Tightly packed in a regular shape
        • The electrons in the outer shell of the metal atoms are delocalised and have strong forces of electrostatic attraction between the positive metal ions and negative electrons
          • Means they conduct electricity and thermal energy
        • Most are solid at room temperature as they have very high boiling points
          • Also malleable because they are arrange in layers and can slide past each other
            • So alloys are created
              • Alloys are a mixture of 2 or more metals or a metal and another element which distorts the layers and makes them strong
    • Nano-particles
      • Nano-particles are extremely small particles
        • Has a high surface area to volume ratio
          • As the side of a cube decreases in size by a factor of 10, its surface area to volume ration increases by 10
      • Applications of nano-particles
        • Can be in the cosmetic industry, sunscreens and on glass to break down dirt
          • Large surface area to volume ratio means they can be used as catalysts but it makes them dangerous because it could cause an explosion

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