Structures

• What happens in ionically bonded substances?

  The oppositely charged ions attract each other from all directions, forming a giant ionic lattice structure containing millions of ions.
• What is a giant ionic lattice?

  A three-dimensional structure of oppositely charged ions held together by ionic bonding.
• Doe ionic compounds have high or low melting/boiling points?

  High
• Why do ionic compounds have high melting and boiling points?

  It takes a substantial amount of energy to break the strong ionic bonds that hold the ions together.
• What happens when an ionic solid melts?

  The lattice breaks down and the ions become free to move.
• Are ionic compounds soluble in water?

  Most ionic compounds are soluble in water and form aqueous solutions.
• What is an aqueous solution?

  A solution in which water is the solvent
• Why do solid ionic solids not conduct electricity?

  In the solid state the ions cannot move and so ionic solids do not conduct electricity.
• What is an electric current?

  A flow of charged particles such as ions and electrons.
• What does molten mean?

  A solid which has melted is described as molten
• Why are ionic compounds good conductors of electricity when molten or dissolved?

  If the ionic solid is molten or dissolved, the ions can move and carry charge.
• Covalent bonding forms substances with two types of structures. What are they?

  Molecular covalent structures and giant covalent structures
• What is a molecule?


  two or more atoms covalently bonded together
• What do molecular covalent structures contain?

  Simple molecules
• What are some examples of molecular covalent structures?

  Iodine, methane and carbon dioxide.
• The structure of molecular covalent structures

  The atoms in molecular covalent structures are held together by strong covalent bonds. Although these bonds are strong, there are only weak intermolecular forces between molecules. These weak attractive forces are called van der Walls' forces of attraction and can be broken with little energy.
• Do molecular covalent structures have high or low melting/boiling points?

  Low
• Why do molecular covalent structures have low melting/boiling points?

  Little energy is needed to break the weak van der Walls' forces of attraction between the molecules.
• What are molecular covalent structures at room temperature?

  Gases, liquids or low melting point solids
• Do molecular covalent structures conduct electricity?

  No
• Why do molecular covalent structures not conduct electricity?

  The molecules are neutral and there are no charged particles (ions or electrons) to move and carry charge.
• What is a giant covalent structure?

  A three-dimensional structure of atoms that are joined by covalent bonds. Such structures are large continuous networks of covalently bonded atoms.
• What are allotropes?

  Different forms of the same element, in the same state.
• Structure of diamond


  Diamond is a giant covalent structure in which each carbon atom is covalently bonded to four other carbon atoms in a tetrahedral, three-dimensional structure.
• What is diamond used for?

  Cutting tools and diamond-tipped tools are used to cut through hard rock, metals and glass.
• Does diamond have a high or low melting and boiling point?High2 multiple choice option
• Why does diamond have a high melting and boiling point?

  Diamond's many covalent bonds are strong and substantial energy is required to break them.
• Does diamond conduct electricity?

  No
• Why does diamond not conduct electricity?

  Diamond has no free ions or delocalised electrons to move and carry the charge.
• What makes diamond hard?

  Diamond's three-dimensional tetrahedral structure with strong covalent bonds makes it very hard.
• Structure of graphite


  Graphite is a giant covalent structure in which carbon atoms are arranged in hexagons, with covalent bonds between the atoms and weak forces between the layers. Each carbon atom is covalently bonded to 3 others, so one electron per carbon atom is unbonded and delocalised and free to move between the layers. It is also three-dimensional.
• What is graphite used for?

  Graphite is used as a lubricant for machinery and in pencils.
• Does graphite have a high or low melting and boiling point?

  High
• Why does graphite have a high melting and boiling point?

  Graphite's many covalent bonds are strong and substantial energy is required to break them.
• Does graphite conduct electricity?

  Yes
• Why is graphite a good conductor of electricity?

  One electron per carbon is unbonded. The unbonded electrons are delocalised electrons, which are free to move and carry charge.
• Is graphite hard or soft?

  soft
• Why is graphite soft and slippery?

  The weak forces between graphite's layers allow them to slide.
• Structure of graphene


  Graphene is a single-atom thick layer of graphite with strong covalent bonds between each carbon atom. The atoms are arranged in hexagons and it is two-dimensional.
• What will graphene be used for and why?

  It is a strong, light and relatively inexpensive electrical conductor and will have many future uses, for example in solar cells and batteries.