Chem 101

• What is the plum pudding model and who proposed it in 1898?

  positively charged mass with negatively charged electrons embedded within it, Thompson.
• what did Rutherford propose in 1911?


  nuclear model - positively charged nucleus with an equal number of negatively charged orbiting electrons
• What were the 3 problems with the nuclear model?

  separated charges will be attracted so the atom would collapse, electrons would eventually stop orbiting as would run out of kinetic energy, energy emitted by the electrons would consist of all light frequencies but this is not what is seen in atomic spectra
• What did Bohr propose and how is this shown?


  electrons posses fixed orbitals, shown by the solid lines in emission spectra
• What does the gaps between the shells being at fixed energy intervals mean?

  the energy given out or taken in is defined
• what does 'n' tell you?

  what shell the electrons are in, e.g. n=1 the electrons are in the energy level closest to the nucleus
• what is Einstein and the photoelectric effect?

  he shone UV light onto a metal surface in a vacuum and observed that electrons were ejected from the metal as a result - demonstrates the quantum behaviour of radiation
• what 4 things did Einstein find from the photoelectric effect?

  1 - the frequency of the radiation must be above a certain threshold for electrons to be ejected. 2 - the threshold is specific to the metal 3 - increasing frequency of the radiation of the threshold doesn't cause more electrons to be ejected but causes them to have greater kinetic energy 4 - increasing the intensity of light increases the number of electrons ejected but not their energy
• what equation can the photoelectric effect be defined as?

  hv = work function + kinetic energy of ejected electron
• what experiment shows that electromagnetic radiation behaves as a wave?

  the double slit experiment
• equation for wave behaviour and particle behaviour?

  E = hv -> wave behaviour E = mc^2 -> particle behaviour
• what equation represents the de Broglie relationship by combining the equations for wave and particle behaviour?


  p = h/lambda, momentum = constant/ wavelength
• what does the de Broglie relationship show?

  it relates wave and particle behaviour
• What is the phase of a wave?


  positive phase is above the x axis, negative phase is below the x axis
• What does it mean for waves to constructively or destructively overlap?

  Constructive overlap is when they overlap in the same orientation so combine to form the same wave, destructive is when they overlap oppositely and so cancel each other into a straight line
• What is the heisenburg uncertainty pronciple?

  because of the way wave interact it van be shown that the error in the knowledge of moments, and position are related by the HUP
• What does it mean if the position is more precisely determined in the heisenburg uncertainty principle?

  the less precisely the momentum is known in this instant
• What is the impact of the Heisenburg uncertainty principle on atomic structure?

  we can't have defined orbits that electrons move in, we instead think about orbitals which define areas of probability of finding an electron
• What quantity describes the schrodinger equation?

  wavefunction, represented by psi (greek letter)
• what does the wave function of the schrodinger wave equation describe?


  the de Broglie waves associated with the particle
• What is the probability of finding an electron at given coordinates?

  psi^2
• what does the quantum number 'L' describe?

  the shape of the orbital. L=0 is an s orbital, L=1 is a p orbital, L=2 is d, L=3 is F
• what does quantum number 'ml' represent?

  the orientation of the orbital. ml= -1,0,1
• Which part of the wavefunction does n and l relate to?

  the radial part
• which part of the wavefunction do l and ml relate to?

  the angular part
• where do s orbitals start in a radial wave function and why?

  they start high as is a sphere around the nucleus and so contains the nucleus
• where do p orbitals start in a radial wavefunction?


  they start low (from 0,0) as it doesn't contain a nucleus
• what is a radial node?


  where the graph crosses the x axis is a radial node
• how do you calculate radial nodes?


  n - l -1, e.g. 5s = 5 - 0 - 1 = 4 radial nodes
• what is an angular node?

  where the graph crosses at 0,0 for a p orbital
• what does a radial distribution tell us?


  the probability of finding electron density at a given point at r distance from the nucleus for an orbital
• what is on the axis of a radial wave function?

  psi on the y and r (the distance from the nucleus)
• can radial wave functions have negative regions?

  no, R(r)^2 means there can be nothing negative
• what is on the axis of a radial distribution function?


  R(r)^2 on y axis and r on x axis
• what does it mean when r = 0, r = small and r = large in a radial distribution function?


  r=0 is a high probability but only one point the electron can occupy, r=small few points with high probability, r=large many points with lower probability
• what is the probability of finding electron density at distance r from the nucleus?

  4pir^2 x R(r)^2 (prob of finding an electron at one point)
• what is the area of maximum probability density dependent on in a radial distribution finction?


  it increases with n but is independent of l
• what is a radial node?

  a distance from the nucleus with zero probability of finding an electron
• what does the maximum point on a radial distribution function show?


  the most probable distance from the nucleus that electron density will be found
• in a radial distribution graph does the shape of the orbital affect where the graph starts?

  no, s and p and d start at 0,0