PHAR1911

• Elements come from stars eg. big bang, cosmic rays, supernovae
• Subatomic particles


  • Proton
  • Neutron (nucleon)
  • Electron
  • Positron (antielectron)
• Isotopes


  Same number of protons but different number of neutrons
• Isotopes of hydrogen


  • Protium
  • Deuterium
  • Tritium
• To calculate the average atomic mass


  Add the number of nucleons of one stable isotope x natural abundance of isotope + nucleons of stable isotope x natural abundance of isotope = average atomic mass

  
• Bohr Model (1913)


  • Electrons in atoms can only occupy certain energy levels (orbits)
  • Electrons can only exist in these discrete energy levels, not in between them

  
• When an electron moves from one energy level to another


  Energy is absorbed or emitted
• Shielding


  The attractive force between the nucleus and electrons

  
• The greater the change in energy levels (ΔE)


  The shorter the wavelength (λ) of the emitted or absorbed light
• Principle Quantum number (n)

  Describes the size of the orbital
• Angular Momentum Quantum number (l)

  Describes the shape of the orbital
• Magnetic Quantum Number (ml)


  Describes the orientation of the orbital
• Spin Quantum Number (ms)


  Has half integer values: +½ or -½
• In an atom, no two electrons can have the same set of quantum numbers (pauli exclusion principle)

  
• Electron "clouds"


  Probability distribution aka region in space where there is a high likelihood of finding an electron at any given time
• Order of energy of subshells


  • 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p ...
• Determining electron configuration


  1. Pauli exclusion principle

  2. Aufbau principle (building up)

  3. Hund's rule

  
• Number of electrons that can fit in orbitals

  • 2 electrons in s
  • 6 electrons in p
  • 10 electrons in d
  • 14 electrons in f

  
• Electron Configuration Examples


  • H: 1s1
  • He: 1s2
  • B: 1s2 2s2 2p1
• Elements in the same group have the same valence electron configuration and as a result, very similar chemical properties
• Electron state of ions

  • Na: 1s2 2s2 2p6 3s1

  Na+: 1s2 2s2 2p6
• Effective nuclear charge (Zeff)


  Positive charge felt by an electron in a multi-electron atom

  
• Atomic radius


  Decreases across a period, increases down a group
• Ionic radius


  Smaller than atomic radius if positively charged (ie. lose an electron), larger for anions
• First ionisation energy


  Increases across a period, decreases down a group
• Ionisation energy


  The amount of energy required to remove an electron from an isolated atom or molecule
• Electronegativity


  How likely it is for an atom in a compound to attract the electrons of a chemical bond towards itself

  
• 4d and 5d elements have almost the same size due to the 'lanthanide contraction'
• Lithium carbonates are used to treat depression. Too much concentration can damage the kidneys.
• Hypertension (high blood pressure) = heart attack = no.1 killer
• Roles of Group 1 & 2 ions

  • Na+ maintains osmotic balance (correct hydration)
  • K+ in glucose metabolism & protein synthesis
  • Mg2+ involved in transport & hydrolysis of ATP
  • Ca2+ is the cation in structural biominerals (teeth, bones); and nerve & muscle function
• Many transition metals have a wide range of oxidation states and form stable complexes. Consequently they are often found at the active site of enzymes
• Electron Pair arrangements


  • Two electron areas: Atoms at the opposite ends of a line, 180º between areas of electrons, Called linear, E.g. CO2
  • Three electron areas: Atoms at the corners of a triangle, 120º between electron pairs, Called trigonal planar, E.g. BF3
  • Four electron areas: Atoms at the corners of a tetrahedron, 109.5º between electron pairs, Called tetrahedral, E.g. CH4
  • Five electron areas: Atoms at the corners of a trigonal bipyramid, Some electron pairs separated by 120º, others by 90º or 180º, Called trigonal bipyramidal, E.g. PCl
  • Six electron areas: Atoms at the corners of an octahedron, 90º between electron pairs, Called octahedral, E.g. SF6

  
• Examples of transition metals in enzymes


  • Fe2+ oxygen transport (haemoglobin)
  • Cu+ / Cu2+ electron transfer catalysts
  • Zn2+ structural role in enzymes
• Thick line


  In front
• If a system has a lower energy when the atoms are close together, then chemical bonding occurs

  
• If there are lone pairs


  • Remove one 'arm' from the electron area arrangement for each lone pair present

  
• Metals are always found together in minerals and ores
• Electron area


  Distinguished by number of electrons (since it can be linear for both Molecular shape and Intermolecular forces)

  
• Metals in Medicine


  • Lithium carbonates used to treat depression
  • Too much concentration can damage the kidneys
  • Hypertension (high blood pressure) = heart attack = no.1 killer