Week 2

• What is visible light?


  Wave that travels through space from where it's produced to where it's observed at constant speed.
• What are light waves characterised by?

  Their wavelength

  Different wavelengths of light produce different colours
• What type of radiation is light a form of?


  Electromagnet radiation
• Red light wavelength:


  640nm - 720nm
• Green light wavelength:


  500nm - 565nm
• Frequency equation:


  $Frequency=$$speed/wavelength$
• What is the amplitude?


  The max displacement of a wave (height)
• How to calculate intensity?


  Amplitude squared
• What is the wavelength?


  The distance between 2 peaks or troughs of wave
• What happens when 2 waves combine to form a new wave?

  • If waves not perfectly aligned with eachother, intensity of resulting wave will be smaller
  • If peaks align, new wave will have double the amplitude
  • If peaks of 1 wave match with troughs on the other, waves cancel out
• What is the phase difference?


  Distance/position between 2 waves

  Between 0-360 degrees
• What does light consist of?

  Stream of particles (photons (packs of energy) travelling to observer
• How do you calculate energy of a photon?


  Energy of a photon = planck's constant * speed of light/ wavelength

  E =hV (V directly proportional to photon energy)
• What is the uncertainty principle?


  Impossible to know exact position & energy of a particle simultaneously e.g, an electron
• How can you model the uncertainty in position of an electron?


  Consider it as a wave with its energy spread out in accord with the shape of the wave.
• The more nodes in the wave...

  The higher the energy

  (when wave crosses axis it changes its sign from + to -)
• What determines an electron's energy level?


  Number of nodes in electron's wave
• How many nodes in level 1?


  0
• How many nodes in energy level 2?


  1
• How many nodes in energy level 3?


  2
• What are orbitals?


  Regions in space where electron likely to be found
• Describe a D orbital:


  Up to 10 electrons

  2 nodes

  6 shapes (only 5 directions so take average of 2 directions) spread evenly over 3 axes:

  dxy, dxz, dyz, d x2-y2, dz2-x2, dz2-y2
• What do the orbital shapes look like?


  :

  
• Describe an S orbital:


  1 or 2 electrons

  Spherical (not directional)

  Has hidden nodes in 2S & 3S but don't affect orbital shape

  ml= 0

  
• Describe a P orbital:

  Up to 6 electrons

  1 node

  Point in 3 directions, orbitals evenly spread

  (px, py & pz)

  ml= -1, 0, +1

  
• Describe a D orbital:


  Up to 10 electrons

  2 nodes

  6 shapes (only 5 directions so take average of 2 directions) spread evenly over 3 axes:

  dxy, dxz, dyz, d x2-y2, d z2-x2, dz2-y2

  ml= -2, -1, 0, +1, +2

  
• What does the dz2 orbital look like?


  :

  
• Which orbitals have directions?

  3p as there's only 3 directions & 5d as there's only 5 directions that d orbitals are allowed to exist
• What is the internal spin of an electron?

  Up or down

  spin quantum number (ms)= + or - 1/2
• What is the principle quantum number?


  Energy level

  n= 1, 2, 3...

  n= number of nodes + 1
• What is the orbital shape quantum number?


  Azimuthal quantum number

  l= 0, 1... (n-1)
• What is the magnetic quantum number?


  Orbital direction

  ml= -1, 0, +1...
• What are degenerate orbitals?


  Orbitals with the same energy.
• Why are only 2 electrons allowed in an S orbital?


  If there were 3, 2 of them would have same set of quantum numbers (not allowed)
• What is the Aufbau rule?


  Electrons occupy lowest energy orbital available
• What is the Pauli principle?


  Max 2 electrons per orbital (1 spin up & 1 spin down)
• What is Hund's rule?


  For orbitals with same energy, orbitals occupied singly if possible (helps to spread electrons as they repel).
• How are excited state arrangements formed?


  Atoms absorb energy