C2 - BONDING

• Ion

  A charged particle, could be a single atom or a group of atoms
• Formation of ions

  1. Atoms gain or lose electrons

  2. To have a full outer shell

  3. For stability
• Group number

  Tells us how many electrons the atoms of that group have in the outermost shell
• Atoms need to lose or gain electrons


  To become stable
• Losing and gaining electrons

  Requires energy
• Group 1 elements (alkaline metals)


  • Only have to lose 1 electron to have a full outer shell
  • Easily lose that electron to become 1+ ions
• Group 2 elements

  • Can easily lose 2 electrons to become 2+ ions
• Group 6 elements

  • Gain 2 electrons to become 2- ions
• Group 7 elements

  • Have to gain 1 electron
• Groups 3-5 elements

  • Would have to lose or gain 3-4 electrons, which requires a lot of energy, so they don't form ions often
• Representing ion formation in chemical equations


  1. Atom goes to form ion + electron (if losing electrons)

  2. Atom + electron goes to form ion (if gaining electrons)
• Representing ions with multiple electrons lost/gained

  Atom goes to form ion + multiple electrons
• Magnesium forms a 2+ ion and 2 electrons
• Oxygen forms a 2- ion by gaining 2 electrons
• Groups 1, 2, 6 and 7 form ions very easily. This is because they only need to gain or lose a small number of electrons, and so less energy is required. 
• Those in groups 3, 4 and 5 do not form ions very easily, because they need to gain or lose a larger number of electrons, and therefore more energy is required. 
• Ions with opposite charges will attract each other. 

  This force of attraction between oppositely charged ions forms an ionic bond. 
• Oppositely charged ions attract each other. 

  This is called an electrostatic force. This same force is also what attracts protons to electrons within atoms and ions
• When drawing dot and cross diagrams, remember to surround the ion with square brackets and put the charge in the top right corner. 
• Metals normally form ions which have a positive charge, while non-metals form ions with a negative charge.

  Ions are attracted to other ions with the opposite charge, due to electrostatic forces. 
• Ionic compounds have relatively high melting and boiling points. 

  This is because ionic bonds are very strong, and a high amount of energy is required to break the bonds
• Solids

  Have a very thick structure, atoms may wiggle a little but are in fixed positions, cannot flow or be compressed
• Liquids

  Have more movement than solids, can flow but cannot be compressed
• Gases

  Have a lot of movement, not in fixed positions, can flow and be compressed
• Boiling point = condensing point, melting point = freezing point
• State symbols

  S = solid, L = liquid, G = gas, Aq = aqueous
• If a liquid and solid or liquid and gas are combined, it will result in cloudiness or bubbles/loss of mass
• Ionic bonding


  Transfer of electrons from a metal to a non-metal
• Ionic charges

  • Group 1 = +1, Group 2 = +2, Group 6 = -2, Group 7 = -1
• Forming ionic compounds

  1. Non-metal keeps its electrons, metal transfers electrons to non-metal

  2. Draw dot-cross diagrams and indicate charges
• Covalent bonding


  Sharing of electrons between two non-metals
• Metals

  Made of positive metal ions in a sea of delocalized electrons, allowing electrical and thermal conductivity
• Alloys


  Contain metal ions and delocalized electrons, plus other elements, resulting in distorted layers that cannot slide
• Pure metals vs Alloys

  • Pure metals have layers that can slide, making them soft
  • Alloys have distorted layers that cannot slide, making them hard
• Ionic compounds

  Have a giant ionic lattice structure, high melting/boiling points, only conduct when molten or dissolved
• Simple covalent compounds

  Have small molecular structures, low melting/boiling points, generally gases or liquids at room temp, do not conduct
• Giant covalent compounds

  Have a giant covalent structure, high melting/boiling points, do not conduct or dissolve
• Giant covalent compounds

  • Diamond, graphite, fullerenes
• Diamond


  • Made of pure carbon, each carbon bonds to 4 others, incredibly hard
• Graphite

  • Made of pure carbon, each carbon bonds to 3 others, soft and conducts electricity