Chemistry paper 1 AQA

• Giant covalent bonding:

  has structure of repeating units of atoms to make giant molecules
• Diamonds and silicon dioxide are examples of giant covalent structures
• Giant covalent structures have very high melting points- lots of energy needed to break the many strong covalent bonds
• Alloys are a mixture of metals that have different size atoms. these cause the layers of the lattice To be disrupted and so cannot Slide Over one another
• Ionic bonding: oppositely charged ions attracted to one another, non-metals and metals
• In ionic bonding, the metal always loses its outer shell electrons to form a positive ion
• Metals in ionic bonding always have an empty outer shell
• Charges of all ions in an ionic compound must add up to 0
• Relative charge of a proton: +1
• Relative charge of a neutron: 0
• Relative charge of an electron:-1
• Relative mass of a proton and neutron: 1
• Relative mass of an electron: very small
• Ions have strong electrostatic forces between bonds, in ionic substances
• Positive ions are known as Cations
• Negative ions are known as Anions
• Ionic compounds make salts
• Ionic structure: positive ions arranged in a lattice of repeating units with a sea of delocalised electrons around it
• Crystals can be formed via ionic bonding
• Ionic structures conduct electricity when molten or aqueous
• Ionic structures can conduct electricity because their ions are free to move and carry charge-this happens in electrolysis
• Metallic bonding: forms a lattice of positive ions surrounded by a sea of delocalised electrons
• Because electrons are free to move in metals, they are good conductors of electricity and heat
• Allotropes: structures made of the same element but arranged differently

  I.e: diamond and graphite
• Diamond structure:

  •giant covalent structure

  •each carbon atom joined to four other carbon atoms by strong covalent bonds

  •the atoms form a regular tetrahedral network structure
• Graphite structure:

  •delocalised electrons form weak bonds between layers

  •these are able to carry charge through structure and so conducts electricity

  •layers slide past one another due to the weak bonds between layers causing it to be slippery
• Graphene: one layer of carbon
• How are fullerenes useful: due to their high surface to volume ratio, fewer are needed for their purpose
• If you double the length of a fullerene, it halves the surface area to volume ration
• Nanoparticles: 100-2500nm
• Coarse particles such as dust are larger than 2500nm
• Fullerenes:

  •used for delivering drugs around the body or other medical purposes

  •strong covalent bonds

  •spherical molecules of C^60

  •not giant covalent structure but have large molecules

  •weak intermolecular forces

  •little energy needed to overcome these

  •slippery

  •low melting point

  •hollow
• Neutrons we’re last to be discoreverd
• JJ Thomson created the plum pudding model- ball of positive charge negative electrons embedded in it
• Ernest Rutherford discovered nucleus was small and positively charged

  -alpha particle scattering experiment, alpha particles went through gold foil and very few were deflected proved this
• Neils Bohr deduced electrons exist in shells and orbited the nucleus
• James Chadwick determined nucleus contained neutrons
• Every bond requires a specific amount of energy to break, it is also the same amount of energy released when the bond is formed
• If there is more energy released than needed to break bonds it is exothermic, the opposite is endothermic
• Non metals bond covalently