atomic structure

• How to answer missing percentage for mass spec abundance calc

  1 Everything equal to AR.mass multiply abundance.missing abundance is x or for two missing its x and whatever percetange is left from what the atom make up)-x.all under 100 (only if its percentages)

  2 solve for x -mass multiply x e.g 5 x x =5x - the mass(in this case 5) is found by minus 100 from other percentages. ect. if its 2 missing abundance put all the x's together when solving.

  3 solve x .deduce 90-x by minus 100 from missing percentage.
• Reading the mass spec:

  ratio is highest to lowest val - e.g cl 37 1/3 of cl 35 so ratio is 3:1
• calculating ar of sample using mass spec

  1 )make a scale if there isn't one

  2)do regular RAM equation(massxabundances)/100
• equation for KE


  KE=1/2 mv^2
• equation for v(velocity)


  v=d/t
• equation to find time from distance,mass,velocity and KE

  t=d√m/2KE
• equation to find mass from KE ,time and distane

  m=2KE t ^2/d^2
• equation for comparing two ions-mass spec

  m1/t1 ^2 = m2/t2^2
• how to use comparing ions eq

  cross multiply on both sides then solve for x or x^2
• how to turn ratio to pecentage abundnce

  1 )add ratios

  2)find percentages of each ion by their part of the ratio divided by total ratio number mulitiplied by 100.

  2)then do RAM equation
• how to find ratio of isotope

  1 find mass from m1 eq

  2 do RAM equation - x and 90-x all over 100

  3 convert percentage to ratio e.g. two percentages are 80 and 20-simplify so 4:1
• tof calculations to find tof + mass

  find by mass by mr divided by avogardos constant divided by 1000

  use regular m1 equation using mr of the ion
• Describe the process of electrospray ionisation


  1)Sample is dissolved in a volatile,polar solvent 2)It's injected through a fine hypodermic needle giving fine mist 3)The tip of the needle has high voltage,here the sample molecule gains a H+ from the solvent forming(molecule H+).
• Equation for electrospray ionisation using x as molecule


  X(g)+H+-/XH+(g)
• blocks on periodic table


  H,He,group 1 and 2-s block transition metals-d-block other groups-p-block
• trends across a period

  -increasing nuclear charge(more protons) -atomic radius-increases-weaker force of attraction -shielding-similar shielding
• trends in IE across a period


  -period3-general increase(nuclear charge increase+atomic radius decreases) but dip in 3 to 5:Mg electron from s orbital,Al electron from p-orbital-p orbital of a higher energy level than s-easier to remove 5 to 6:P electron from orbital with one e- sulfur e- from orbital with two electrons-greater electron repulsion-easier to remove.
• Why do successive ionisation energies get larger?

  Once you have removed the first electron you are left with a positive ion. Successive ionisation energies increase because electrons are removed from an increasingly positive ion, which requires more energy.
• What are CFC's?


  chlorofluorocarbon compounds-contain only those elements.
• uses of CFCS

  -propellents in aerosol,solvents,refridgerants
• what is the purpose of the ozone layer?


  protect us from harmful UV light.
• describe the decomposition of ozone by CFCs


  When CFCs are released into the atmosphere they are exposed to UV rays.Their bonds are broken to form free radicals.These react with ozone to form oxygen which doesn't protect us from the ozone layer.
• what determines the radical formed?


  biggest bond enthalpy(flourine biggest) in group 7
• overall equation for decomposition of ozone


  2O3 ---/ 3O2
• what is chlorine's role in the decomposition of ozone


  acts as a catalyst(speeds up the reaction and is regenerated at the end).
• steps for free-radical substitution of ozone


  1. initiation-chlorine radical formed from CFC and CFC lost cl 2)propagation-chlorine radical+ozone to give ClO radical and oxygen 3)propagation 2- ClO radical +ozone to give cl radical and 2O2 4)Termination-product formed from radicals
• alternative to CFCs

  hydrocarbons or hydrofluorocarbons-higher bond enthalpy-won't break when exposed to UV so free radicals won't form.
• Why is electrospray ionisation used instead of electron impact for the ionisation of a protein in a mass spectrometry experiment.


  The protein does not break up.
• electron impact equation


  X (g) +e- → X+ (g) + 2e-
• mass spec main points 


  mass spec