step 1: Vapourtion, if sample is solid its vaporised by heating

step 2: ionisation, beam of electron from an electron gun knocks out electron from atom/molecules to form +ve charged ions 

step 3: Acceleration, +ve ions attracted by -ve charged plates & accelerated at high speed. lighter ions reach first

step 4: Deflection, beam of ions move into magnetic field at right angle to it direction of tavel, magnetic field deflect it into an arc of circle. lighter ions defleted more 

step 4: Detection, magnetic field gradually increased so ions of incresing mass enter, ions strike detector gain an electron & becomes -ve. computer works out it mass spectrum.


(% x mass) + (% x mass)

______________________    = ?



Electron arrangement in atoms (orbitals)

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ionisation energy

  1. Ionisation enery is the energy needed to remove 1 mole of electrons from 1 mole of 1 mole of atom in it gaseous state 
  2. First ionisation s energy needed to remove1 electron from a neutral atom 

Equation (= + at the top) 

1st IE   atom(g) ----> atom (g) + e- 2nd IE     atom*(g) ---> atom2* (g) + e-

eg.       Na(g) ----> na*(g) + e-

ionisation energy decreases s you go down the group, this is because;

  • group tells you the number of electrons on the outer shell, priod tells you how many shells 
  • as you go down the groups the eectrons gets furter away from the nuclers o easier to ionise 
  • as you go down the group the period increases, therefore more shells acting as elctron shielding

why is it that as we go from magnesium to aluminium the ionisation energy decreases?

  • because the outer electron for magnesium is in 3s(2) ortibal and the orbital is full 
  • whereas the outer electron for aluminium is in 3p(1) orbital and is not full(only 1 electron) so its easier to lose.

why is it that a the ionisation energy for phosphorus is higher that sulfur ?

  • because in phosphrus each of the 3p orbital contain just 1 electron so no repulsion 
  • whereas in sulfur 1 of the 3p orbital has 2 electron so there's repusion between the two electrons
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Amount of substance

                                                                          average mass (g) element

  •            relative atomic mass (Ar) =                       --------------------  = Ar

                                                                           mass of atom 

                    eg  H2O (H=1.0,  O=16.0,)  

                          H20 = (2X1.0) +16.0 = 18.0 Ar

                                                                               average mass (g) molecule

  •            relative molecular mass (Ar) =                     --------------------  = Mr

                                                                                 mass of atom 

                           eg  H2O (H=1.0,  O=16.0,)  

                     H20 = (2X1.0) +16.0 = 18.0 Mr

  • Avogadro constant is the number of atom in 12g of C-12.          6.022x10 (to the power 23)
  •                       # of Moles =  mass (gram) given

                                                             ------------------      = mol

                                               mass of atom (periodic table)

                                        eg how many moles in 64.2g f sulfur (S)? Ar S = 32.1 


                                                       -------    = 2.00 mol


  •                      The ideal GAS equation:   PV= nRT   Pressure Pa,Volume M(3),n=mole,temp K +273 ,R=8.31

Eg temp = 20.0 C (293.0 K), Pressure = 100,000Pa, and n = 1 or 1 mole of gas, R = 8.31

V? = nRT/P    V= 1x8.31x293.0

                        -------------- =


Concentration = moles x 1000



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