bonding, structure and matter - topic 2

• Ions


  • Charged particles
  • Metal ions = Lose electrons to form positive ions
  • Non-metal ions = gain electrons to form negative ions
• Ionic Bonding


  Formed when metal and non-metal react together – attracted by an electrostatic force of attraction between oppositely charged ions
• Empirical formula


  Simplest whole number ratio of atoms of each element in compound
• Ionic Compounds


  • A giant structure called 'lattice'
  • Held by an electrostatic force of attraction
  • Forces act in every direction, 3D
• Properties of ionic compounds

  • High melting/boiling points (strong bonds)
  • Can't conduct electricity when solid (when melt – free to move so they carry a charge)
  • Some dissolve in water
• Covalent Bonding


  When 2 non-metal atoms bond together they share electrons (shared pair)
• Covalent Bonding


  • Positively charged
  • Attracted by intermolecular forces – strong bonds
  • Only share electrons in outer shell
• Covalent bonding models don't show relative size or arrangement
• Good 3D models


  • Show the atom
  • Show the covalent bonds
  • Show arrangement
• Bad 3D models


  • Can confuse large molecules
  • Don't show where bonds form
• Metallic Bonding


  • Electrons in the outer shell are delocalised – not associated with an atom or a single bond
  • Strong forces of electrostatic attraction – between positive metal ions and shared electrons
  • Malleable and Ductile
• States of matter


  1. Solid – liquid = melting

  2. Liquid – gas = boiling

  3. Liquid – solid = freezing

  4. Gas – liquid = condensing

  5. Gas – solid = deposition

  6. Solid – gas = sublimation
• State symbols


  • Dissolved in water: aq
  • Liquid: l
  • Solid: s
  • Gas: g
• Properties of simple molecular substances

  • Doesn't conduct electricity
  • Low melting/boiling points – weak intermolecular forces
• Polymers


  • Long chains of repeating units
  • Form long molecules
  • Strong covalent bonds
  • Intermolecular forces – larger than big covalent bonds (more energy needed to break them) (weaker than ionic or covalent bonds)
• Repeating unit: Polythene


  • =(C2H4)n
• Nano-particle


  • 1nm-100nm
  • Might not be safe
• Giant Covalent Structures


  • Bonded by strong covalent bonds
  • High melting/boiling points – lots of energy needed to break bonds
  • Don't conduct electricity
• Giant Covalent Structures


  • Diamond
  • Silicone dioxide
  • Graphite
• Properties of metals


  • High melting point – strong forces
  • Solid at room temp
  • Good conductors – delocalised electrons carry electrical and thermal charge through the structure
  • Malleable and ductile – Layers of pure metal can slide easily over each other
• Properties of Alloys


  • A mixture of two or more elements (one = metal)
  • Different elements have different-sized atoms – distorted layers so cannot slide easily over each other
• Allotropes of carbon


  Different structural forms of carbon
• Diamond


  • Very hard
  • Carbon atoms
  • 4 covalent bonds
  • High melting bond – strong bonds to break
  • Doesn't conduct electricity – no electrons to carry a charge
• Graphite


  • Sheets of hexagons
  • Carbon atoms
  • 3 covalent bonds
  • Sliding layers, held together weakly – soft and slippery
  • High melting point – strong bonds to break
  • 1 delocalised electron to carry a thermal and electric charge (conducts)
• Graphene


  • One layer of graphite
  • Joined together by hexagons
  • Conducts electricity – delocalised electrons
  • High melting point – strong bonds to break
• Fullerenes


  • Carbon atoms
  • Hollow ball or closed tube (arranged in pentagons, hexagons and heptagons) – Buckminsterfullerene (first to be discovered)
  • Used to cage other atoms
  • Conducts electricity – delocalised electrons