Bonding and structure

• ionic bonding


  Oppositely charged ions held together by electrostatic attractions
• Swap and drop method


  Write the two ions

  Swap charges

  Drop charges

  Simplify to the nearest whole number
• Ionic compounds


  Giant ionic structure

  Regular structure

  Cubic shape

  Giant repeated pattern
• ionic compound


  Most dissolve in water as water molecules are polar.

  Conduct electricity when molten or dissolved in a solution (ions free to move).

  Have high melting points (strong electrostatic forces, lots of energy needed to break them)
• covalent bonding


  Sharing of outer electrons

  Electrostatic attraction between shared electrons & nucleus

  Single, double, triple covalent bonds

  Can be represented as lines
• Dative covalent bond


  Where one atom donates 2 electrons to an atom or ion to form a bond

  Can be represented as an arrow in displayed formula
• Water molecules


  Polar, can attract the positive and negative ions and break up the structure.
• Shapes of molecules


  Linear, original planar, tetrahedral, pyramidal, non-linear, trigonal bipyramidal, octahedral
• Molecules (shape)


  Have specific shapes, bonds repel each other equally, want to be as far away as possible
• lone pair


  a pair of electrons that is not involved in bonding and that belongs exclusively to one atom
• lone pair - bonding pair


  Will repel more than 2 bond pairs together

  2 lone pairs will repel even further

  For every lone pair the remaining bond angle is reduced by 2.5 degrees
• bond pair


  an electron pair shared between two atoms
• octet rule


  States that atoms lose, gain or share electrons in order to acquire a full set of eight valence electrons
• Expanding octet


  Groups 15-17 from period 3 downwards

  More electrons in valance
• Shrinking octet


  Cases where there aren't enough electrons to form an octet