Chemistry unit 1

• When analysing markets, a range of assumptions are made about the rationality of economic agents involved in the transactions
• The Wealth of Nations was written

  1776
• Rational


  (in classical economic theory) economic agents are able to consider the outcome of their choices and recognise the net benefits of each one
• Rational agents will select the choice which presents the highest benefits
• Consumers act rationally by


  Maximising their utility
• Producers act rationally by


  Selling goods/services in a way that maximises their profits
• Workers act rationally by


  Balancing welfare at work with consideration of both pay and benefits
• Governments act rationally by


  Placing the interests of the people they serve first in order to maximise their welfare
• Rationality in classical economic theory is a flawed assumption as people usually don't act rationally
• If you add up marginal utility for each unit you get total utility
• There is much variety of life within and between organisms but the biochemical basis of life is similar for all living things
• Key molecules required to build structures that enable organisms to function

  • Carbohydrates
  • Proteins
  • Lipids
  • Nucleic Acids
  • Water
• Monomers


  Smaller units from which larger molecules are made
• Polymers


  Molecules made from a large number of monomers joined together in a chain
• Synthetic polymers


  • nylon
  • polyethylene
  • polyester
  • Teflon
  • epoxy
• Enzyme catalysis


  1. Substrate binding

  2. Transition state facilitation

  3. Catalysis

  4. Release
• Enzymes


  • They increase the rate of chemical reactions without themselves being consumed or permanently altered by the reaction
  • They increase reaction rates without altering the chemical equilibrium between reactants and products
• As temperature increases


  The rate of reaction increases
• The basic model of the atom has two main components – the positively charged nucleus, which contains positive protons and neutral neutrons, and the cloud of negatively charged electrons which encircle it
• In all atoms, the number of protons equals the number of electrons
• Protons and neutrons are far larger and heavier than electrons
• Bohr model of the atom

  Electrons are arranged in shells around the nucleus, which have higher energy levels as you move further away from the centre
• Each shell has a maximum number of electrons that can fit into it – once it is full, extra electrons must go into the next shell
• Shells and orbitals


  • 1 shell (1 × s orbital)
  • 2 shell (1 × s, 3 × p orbitals)
  • 3 shell (1 × s, 3 × p, 5 × d orbitals)
  • 4 shell (1 × s, 3 × p, 5 × d, 7 × f orbitals)
  • 5 shell (1 × s, 3 × p, 5 × d, 7 × f, 9 × g orbitals)
• Aufbau principle


  Electrons fill the lowest available energy shells first, and singly occupy orbitals in the same energy level before pairing up
• Orbitals are labelled s, p, d or f, depending on which subshell they are in – p orbitals are higher in energy than the s orbitals in the same shells, d orbitals are higher than p orbitals, and so on
• The most stable electron configuration is obtained by arranging electrons according to the rules for filling orbitals
• Ionic bonds are formed from the electrostatic attraction between oppositely charged ions
• Ions


  Atoms that have lost or gained electrons, becoming positively or negatively charged
• By exchanging electrons, both elements are able to achieve a full outer shell of electrons, which is the most stable electronic configuration
• The ratio of positive ions to negative ions does not have to be 1:1, e.g. in MgCl2
• Giant ionic lattice


  An arrangement of negative ions and positive ions in a regular 3D pattern
• Factors affecting ionic bond strength

  • Ionic charge
  • Ionic radius
• Smaller ions with higher charges result in stronger electrostatic attractions
• Covalent bonding


  Sharing of electrons rather than complete exchange from one atom to the other, most common between non-metals
• The sharing of electrons is done to give each atom involved a full outer shell of electrons
• The stronger a covalent bond is, the shorter the bond length is
• Stronger covalent bonds are a result of the two bonding atoms having a large difference in electronegativity
• Multiple bonding


  More than one pair of electrons must be shared in order to reach the noble gas configuration
• Double bonds and triple bonds are stronger than single bonds and, therefore, are also shorter in length