2-Bonding, structure and the properties of matter

• ions are formed when an atom loses or gains an electron, it is an atom with a charge
• losing or gaining electrons requires a lot of energy so it is easier and more likely to gain or lose 1-2 electrons rather than 3-4
• half equations to represent the gain or loss of electrons:

  • place electron on the right when electron is lost and is forming positive charge
  • Na → Na+ + e-
  • place electron on the left when electron is being gained and is forming negative charge
  • O + 2e- → O²- .
• ionic bond

  • it is a transfer of electrons between opposite charges that are attracted to each other by electrostatic forces
  • the electrostatic forces between these atoms form an ionic compound, the ionic bond is really strong
  • dot and cross diagrams can be used to represent the electrons, the atoms should be surrounded by brackets and have a positive or negative charge with the number of electrons lost or gained
  • it creates neural overall change
• ionic compounds form regular lattice structures as ionic bonding usually involves many ions, each ion is attracted to all those around it as the positive and negative ions alternate
• properties of ionic compounds:

  • they have high melting and boiling points due to the strong ionic bonds that need lots of energy to break
  • they can conduct electricity while molten or dissolved in water due to the ions being free to move
• formula of an ionic compound

  • the charges of ions balance out
  • hydroxide ion - OH⁻
  • sulphate ion- SO₄²⁻
  • nitrate ion- NO₃⁻
  • carbonate ion- CO₃²⁻
  • ammonium ion- NH₄⁺
• covalent bonds

  • share electrons
  • are between non-metal elements
  • can be drawn by dot and cross diagrams
  • displayed formula e.g. Cl-Cl
  • pro: easy to draw big molecules con: doesn't present the 3D structure
• types of substances covalent bonds can make

  • simple
  • giant covalent structures
• properties of simple covalent structures

  • strong covalent bonds between atoms
  • weak intermolecular forces between molecules
  • low melting/boiling point due to weak intermolecular forces
  • cannot conduct electricity as they have no free electrons
• properties of giant covalent structures

  • arranged in repeating lattices
  • strong covalent bonds between atoms
  • no weak intermolecular forces as there's only one structure
  • high melting/boiling point due to having lots of shells
  • cannot conduct electricity except graphite
• allotropes are substances made from the same element in the same physical state but with different structures
• allotropes of carbon:

  • diamond
  • graphite
  • graphene
  • fullerene
• properties of diamond

  • giant covalent structures (regular lattice, covalent bonds)
  • very strong, high melting/boiling point, does not conduct electricity
  • each carbon atom is covalently bonded to 4 other carbon atoms
• properties of graphite

  • are arranged into hexagons that stack, these layers are held by weak intermolecular forces so can slide
  • giant covalent structure (regular lattice, covalent bonds)
  • soft, high melting/boiling point, conducts electricity (1 free/delocalised electron)
  • each carbon atom is covalently bonded to 3 other carbon atoms
• graphene

  • is one layer of graphite
  • same properties as graphite- strong, can conduct electricity
  • can be formed into fullerenes- tubes, spheres
  • industrial catalysts- large surface area: volume
  • spheres can be used to encase drugs and deliver them to the body
  • tubes- known as nanotubes and can be used in nanotechnology and electronics to conduct electricity, used to strengthen other materials
• bonding

  • metallic- between metals
  • ionic- between metals and non-metals
  • covalent- between non-metals
• metallic bonds

  • giant structure of atoms arranged in a regular pattern
  • electrons are shared with other atoms, making the atoms positive
  • the electrons are delocalised so metal can conduct heat and electricity
  • strong electrostatic attraction between electrons and atoms
  • they are malleable due to the layers sliding over each other
• alloys

  • contain two or more different elements
  • can be used to make harder metals
  • they will have different size atoms as it will disrupt a metal's regular structure, preventing sliding between layers
• particle theory

  • each particle is a small, solid, inelastic sphere
  • solids- strong forces of attraction(bonds), vibrate in a fixed position, have definite shape and volume
  • liquids- weak forces of attraction, free to move around, fairly compact, don't have definite shape but have definite volume
  • gases- very weak forces of attraction, free to move around by themselves, don't have definite shape or volume
• State symbols show the physical state molecules are in

  • s is solid
  • l is liquid
  • g is gas
  • aq is aqueous (dissolved in water)