Ozone story

• Human activities that increase carbon dioxide levelsthat increase carbon dioxide levels

  • combustion of hydrocarbon fuels, power stations
  • deforestation
• How does human acts increase methane in air

  • cattle farming
  • landfill sites
  • rice paddy fields
• Human activities increasing nitrous oxide

  • Fertilised soils
  • changes in land use
• human acts increasing carbon monoxide

  incomplete combustion of hydrocarbons, car exhaust
• human acts increasing nitrogen oxides


  internal combustion engines, N2 and O2 at high temperatures
• calculating percentage composition you divide by 10,000
• calculating concentration in ppm, take the sample percentage x10,000
• When electromagnetic radiation reacts with matter it transfers energy
• E=hv

  c=lambda v
• ways molecules motion is dependent on the energy

  • translation- molecule moving around
  • rotationn- microwave 1x10^-22 to 1x10^-20
  • vibration- infrared 1x10^-20 to 1x10^19
  • elctectron energy- visible + UV 1x10^-19 to 1x10^-16
• Electronic energy is quantised, it has fixed levels
• The numerical intermediates are due to the strength of. different bonds will require different energies in order to vibrate
• What happens when a molecule such as Cl2 absorbs UV radiation

  • Cl2 outer shells are in a high energy level, can easily move into a high Energy level
  • its also dependent on the amount of energy involved
  • electrons may be excited to a higher energy level
  • high energy radiation - molecule absorbs too much energy that the bonding electrons BREAK, this is photodissociation, radicals are formed
• photodissociation is where high energy radiation is emitted onto a molecule meaning its bonding electrons break, it forms radicals
• radicals are molecule/atoms with an unpaired electron
• Radicals are highly reactive and produce chemical reactions
• High energy photons, molecule has too much energy that an electron can leave it. it is ionised
• Electronegativity increases across a period and up a group towards Fluorine
• Fluroine is the most electronegative element
• Electronegativity predicts how polar a covalent bond will be, C-F fluroine being more electronegative than C so attracts bonding electrons more strongly
• Electronegativity is the measure of the ability to attract bonding electrons in a covalent bond to itself, an atom
• • longer the chain, the stronger the intermolecular forces, greater the boiling point
  • more contact between molecules in a straight chain, more intermolecular bonds form, more surface contact. increases boiling point, opposite for branched molecules
• explain the origin of instantaneous induced dipole

  • Electrons in atoms moving at high speeds in orbitals
  • possible for electrons to be more at one side than equality in the middle as they move
  • one side becomes slightly negative, other is slightly positive, delta
  • this produces a dipole, where it can now induce another neighbouring molecule
• a dipole is a molecule that has a positive end and a negative end, polar bonds
• with a smaller core, there’s a greater core charge, so the electrons are more strongly attracted to the nucleus. creating a dipole (polar bond permenant) , larger attraction
• shared electrons are attracted strongly by the core of a smaller atom, atom with greater core charge. that atom becomes delta negative due to its greater electronegativity. This can affect their physical properties
• explain origin of permanent dipoles


  they occur when two atoms in a bond have substantially different electronegative, H-Cl, O-H
• How to know if a molecule is polar?

  • difference in electronegativity, though dependent HEAVILY on shape
  • may have polar bond, but overall a molecule can be. superimposed by shape and is a non-polar molecule
• instantaneous dipole is temporarily, electrons are in constant motion within a bone, may not be equally distributed so one end has greater delta negative an delta positive end- Cl2
• induced dipole is where an unpolarised molecule is near a dipole molecule
• The intermolecular bond is stronger when there’s greater electrons, greater boiling point
• an induced dipole induces another molecule by the electrons attracted to delta positive side of molecule
• What’s the strongest intermolecular bond


  hydrogen bonding
• Hydrogen bonding, a large dipole between H atom and highly electronegative atom ONLY: F,N,O
• lone pair of electron on F,N,O lines up with the delta positvley charged H atom
• small H atom strongly attracts because of its smaller core
• the delta positive H linens up with the lone pairs on the O atoms
• Hydrogen bonding has the greatest boiling point regardless of molecular mass
• O has x2 lone pairs and can form 4 hydrogen bonds per molecule
• Bond fission is bond breaking, which redistributes the electrons in the covalent bond