structure and bonding gcse aqa

• which groups easily form ions?


  1,2,6,7

  
• What are giant covalent substances primarily composed of?

  They consist of atoms linked by strong covalent bonds.
• Why do giant covalent substances have very high melting points?

  Because strong covalent bonds must be overcome to melt or boil them.
• Name two examples of giant covalent structures.

  Diamond and silicon dioxide (silica).
• How many covalent bonds does each carbon atom form in diamond?

  Each carbon atom forms four covalent bonds.
• What properties make diamond very hard?

  Its structure consists of strong covalent bonds between carbon atoms.
• Why does graphite have a high melting point?

  Because it has strong covalent bonds between carbon atoms.
• What allows graphite to be soft and slippery?

  The layers of carbon atoms can slide over each other due to no covalent bonds between them.
• What is the role of delocalised electrons in graphite?

  They allow graphite to conduct thermal energy and electricity.
• What is graphene?

  Graphene is a single layer of graphite that is one atom thick.
• What are fullerenes?

  Fullerenes are molecules of carbon atoms with hollow shapes.
• What is the structure of fullerenes based on?

  Hexagonal rings of carbon atoms, with possible five or seven-membered rings.
• What was the first fullerene to be discovered?

  Buckminsterfullerene (C60).
• What are carbon nanotubes?

  Cylindrical fullerenes with very high length to diameter ratios.
• Why are carbon nanotubes useful?

  They have properties that make them useful for nanotechnology, electronics, and materials.
• What is the arrangement of atoms in metals?

  Atoms are arranged in a regular pattern forming giant structures.
• What is the significance of delocalised electrons in metals?

  They are free to move through the whole structure, contributing to metallic bonding.
• How do delocalised electrons contribute to the properties of metals?

  They allow metals to conduct electricity and thermal energy.
• What is the effect of strong metallic bonding on the melting and boiling points of metals?

  It results in high melting and boiling points due to the energy needed to break the bonds.
• What is the difference between pure metals and alloys?

  Alloys are mixtures of different metals, while pure metals consist of the same size atoms.
• Why are alloys harder than pure metals?

  The different sizes of atoms in an alloy distort the layers, making it harder for them to slide over each other.
• What term is used to describe the electrical conductivity in metals and graphite?

  Delocalised electrons.
• How do molten ionic substances conduct electricity?

  They have ions that are free to move.
• What are some applications of nanoparticles?

  They are used in medicine, electronics, cosmetics, and materials development.
• What size range defines nanoparticles?

  1–100 nm.
• How do nanoparticles differ from fine particles?

  Nanoparticles are smaller than fine particles, which range from 100 to 2500 nm.
• What happens to the surface area to volume ratio as the side of a cube decreases?

  It increases by a factor of 10.
• Why might nanoparticles have different properties than bulk materials?

  Because of their high surface area to volume ratio.
• What are the benefits of using nanoparticles in sun creams?

  They provide better skin coverage and more effective protection from UV rays.
• What are some disadvantages of nanoparticles in sun creams?

  Potential cell damage and harmful effects on the environment.
• What are the boiling and melting points of different structures?

  • Small molecules: Low due to weak intermolecular forces.
  • Ionic: High due to strong electrostatic forces.
  • Giant Covalent: High due to many strong covalent bonds.
  • Metallic: High due to strong electrostatic forces between positive ions and delocalised electrons.
• How does conductivity differ among various structures?

  • Small molecules: Poor conductivity when solid.
  • Ionic: Poor conductivity when solid, good when molten.
  • Giant Covalent: Poor conductivity when solid (except graphite).
  • Metallic: Good conductivity when solid and molten.
• What are the general descriptions of different structures?

  • Small molecules: Mostly gases and liquids.
  • Ionic: Crystalline solids.
  • Giant Covalent: Solids.
  • Metallic: Shiny metal solids.
• What occurs at the melting point?

  Melting and freezing between solid and liquid take place.
• What determines the amount of energy needed to change state?

  The strength of the forces between the particles of the substance.
• What does particle theory help explain?

  Melting, boiling, freezing, and condensing.
• How do gas particles behave?

  They are widely spaced and in constant quick motion.
• How do liquid particles behave?

  They are closely spaced but still in constant motion.
• How do solid particles behave?

  They can only vibrate in a fixed position.
• How can melting point and boiling point data be used?

  To distinguish pure substances from mixtures.