Bonding, Structure, Properties and Energy

• Within a molecule, each atom is surrounded by areas of electron density. These areas can be bonding areas or lone pairs. These negative areas repel each other and move as far apart as possible
• There are __ areas of electron density around the central atom. Due to electron-electron repulsion (the repulsion of negative/like charges), these areas move as far apart as possible (to the corners of its base shape/in a straight line). Since there are __ bonding areas, and __ lone pairs, the final shape is __, with a bond angle based on (base shape: 180, 120, or 109.5)
• A covalent bond involves sharing of electrons between non-metal atoms, to get a full valence level/shell
• Electronegativity: The force of attraction on atom has for a bonding pair of electrons within a molecule
• Non-polar covalent bond: Where the bonding electrons are shared equally between atoms of the same electronegativity (the same kind of atom)
• Polar covalent bond: Where the bonding electrons are unequally shared. The more electronegative atom has a greater 'pull' on the bonding electrons, resulting in a slightly negative side. The less electronegative atom has a weaker 'pull' on the bonding electrons, resulting in a slightly positive side.
• A non-polar molecule is where there is symmetrical electron density distributions i.e. bond dipoles cancel out.
• A polar molecule is where there is asymmetrical electron density distribution i.e. the bond dipoles do not cancel out
• Exemplar: BF3 contains polar bonds because F is more electronegative than B, resulting in bond dipoles (Delta positive B - Delta negative F)

  Since the shape of BF3 is symmetrical and the bond dipoles cancel out, BF3 is a non-polar molecule
• The melting point is the temperature at which you have supplied the amount of energy required to overcome some of the forces of attraction between the particles, so that the particles can slide past each other
• The boiling point is the temperature at which you have supplied the amount of energy required to overcome all of the forces of attraction between the particles, so that the particles can move independently of each other.