Bonding, structure and the properties of matter

• Ionic bonding


  Attraction between oppositely charged ions
• Ionic bonds


  • Found in compounds made of metals and non-metals
• Covalent bonding


  2 atoms sharing 1 or more pairs of electrons
• Covalent bonds


  • Found in most non-metal elements and in non-metal compounds
• Metallic bonding


  Attraction between positively charged ions and negatively charged delocalised electrons
• Metallic bonds


  • Found in metals and alloys (mixtures of metals and other substances)
• Ions


  Particles that have a charge, created when an atom or molecule gains or loses electrons
• Positive ions (cations)


  Usually created when an atom or molecule loses electrons
• Negative ions (anions)


  Usually created when an atom or molecule gains electrons
• Ions can be made up of

  • 1 atom
  • Combinations of atoms with an overall charge
• Ionic bonding


  1. Metal atom transfers electrons to non-metal atom

  2. Both atoms have full outer electron shell
• Ions formed from Group 1 metals

  Lose 1 electron, resulting in +1 charge
• Ions formed from Group 2 metals

  Lose 2 electrons, resulting in +2 charge
• Ions formed from non-metals (Groups 6 and 7)

  Gain electrons, resulting in negative charge
• Noble gases (Group 0) are unreactive and don't normally form ionic bonds
• Empirical formula


  Simplest ratio of ions in a compound
• Empirical formulae


  • CaF2
  • Na2SO4
• Covalent bonding


  2 non-metal atoms share pairs of electrons
• Covalently bonded substances


  • Small molecules
  • Large molecules
  • Giant covalent structures
• Metallic bonding


  Electrostatic attractions between positive ions and negative delocalised electrons
• Ways of representing covalent bonds

  • Dot-and-cross with shells
  • Dot-and-cross without shells
  • Ball-and-stick
  • Lines
• How sodium fluoride is formed

  1. Sodium atom transfers outer electron to fluorine atom

  2. Resulting in Na+ and F- ions with full outer shells
• How calcium oxide is formed

  1. Calcium atom transfers 2 outer electrons to oxygen atom

  2. Resulting in Ca2+ and O2- ions with full outer shells
• Double and triple covalent bonds

  Stronger and require more energy to break than single covalent bonds
• States of matter


  • Solid
  • Liquid
  • Gas
• State symbols


  • (s) for solids
  • (l) for pure liquids
  • (aq) for aqueous solutions
  • (g) for gases
• Properties of ionic compounds

  • High melting and boiling points
  • Don't conduct electricity if solid
  • Conduct electricity if liquid or in solution
• Intermolecular forces


  Affect the properties of a molecule based on its size
• Small molecules


  • Have weak intermolecular forces, low melting and boiling points, often liquids or gases, don't contain delocalised electrons
• Small molecule


  • Chlorine (Cl2)
• Bigger molecules


  • Have stronger intermolecular forces, higher melting and boiling points, don't contain delocalised electrons
• Bigger molecule


  • Sucrose
• Polymers


  Large, chain-like molecules held together by strong covalent bonds and weak intermolecular forces
• Polymers are usually solid at room temperature but can melt easily
• Polymer


  • Poly(propene)
• Non-metals do not contain delocalised electrons, and so can't conduct electricity
• Sucrose


  Example of a bigger molecule
• Sucrose is made of 45 atoms and has the formula C12H22O11
• Although sucrose is a simple molecule, its size means that its intermolecular forces are strong enough for it to be solid at room temperature
• Polymers


  Large, chain-like molecules that can extend for thousands of atoms