*The Ozone Story

• Electronegativity is the ability of an atom to attract a bonding pair of electrons in a covalent bond towards itself
• Electronegatvity increases along a period and decreases down a group
• A permanent dipole is when two atoms that are bonded have differing electronegativities and draws more of the negative charge towards itself
• Polar molecules arise when there is an overall difference in polarity across a molecule due to polar bonds
• pd-pd attractiosn can align to form a lattice of molecules
• An induced dipole is when electrons are influences by the distribution of electrons on another particle. All molecules have id-id attractions
• The greater the Mr of an atom the greater the id-id forces
• pd-pd attractions are stronger than id-id forces so the melting and boiling points will be higher
• Hydrogen bonding is the strongest type of intermolecular force and forms when a hydrogen is bonded to a NOF (nitrogen, oxygen or fluorine)
• Hydrogen bonds cause much higher melting and boiling points
• Activation energy is the minimum amount of energy needed to begin a reaction
• On a concentration-time graph the rate of reaction is equal to the gradient of the curve at a given point
• Gradient = (change in y)/(change in x)
• A Maxwell-Boltzmann distribution is a plot of the number of molecules against kinetic energy
• Increasing the temperature can cause the Maxwell-Boltzmann distribution to shift to the right
• Concentration, pressure and surface area have no effecr on the Maxwell-Boltzmann distribution
• Catalysts cause the activation energy to shift to the left in a Maxwell-Boltzmann distribution curve
• ppm is parts per million which is equal to 1,000,000 total units of mass
• id-id forces increase down group 7 and this causes the boiling points to increase
• The greater the Mr the lower the bond enthalpy as the bonds cna be broken more easily so rate of reaction for haloalkanes increases down group 7
• Nucleophillic substitution is a functional group being replaced by an electron donor (nucleophile)
• Nucleophilic substitution:

  1. The carbon donates a pair of electrons to the functional group
  2. The nucelophile comes in and donates a pair of electrons to the carbon forming a bond
  3. Ion of functional group displaced is left over
• Homolytic fission is the breaking of a bond by donating an electron to two different atoms forming two radicals (single-headed arrow)
• Heterolytic fission is the breaking of a bond where two electrons go to the same atom forming a positive and negative ion
• A radical is a species that has an unpaired electron
• Alkenes react with halogens in the presence of UV light to form haloalkanes
• Radical reactions:

  • initiation = forming a radical
  • propogation = a radical reacts to form another radical
  • termination = two radicals react to form a molecule
• CFC's are chlorofluorocarbons that are involved in the breakdown of O-zone
• Breakdown of O-Zone:

  1. CF3Cl -> CF3* + Cl*
  2. Cl* + O3 -> ClO* + O2
  3. ClO* + O3 -> Cl* + 2O2

  overall equation = 2O3 -> 3O2

  chlorine is regenerated in the reaction and is therefore a catalyst
• O-zone is found in the stratosphere and it absorbs UV rays which helps prevent skin cance and gene damage. O-zone depletion is largely due to greenhouse gases being released into atmosphere
• Photochemical smog is made by sunlight reacting with nitrogen oxides, other vehicle emissions and O-zone
• Electromagentic specturm:

  • radio waves
  • microwaves
  • Infrared
  • visible
  • UV
  • x-rays
  • gamma rays