1_Atomic structure

1_Atomic structure

1. History

   • Bohr model
     • Positive region in centre
     • Negative electrons orbit
   • 1897 JJ Thompson- discovered electrons
     • And plum pudding model
   • schrodinger
     • equation to predict where electrons are
   • 1911 Rutherford
   • chadwick- discovered neutrons

2. Time of flight mass spectrometer

   • takes place in a vacuum
     • prevents ions from interacting with the air
   • sample is always in gas form
   • allows scientists to identify isotopes/atoms in unknown solution
     • identifies molecular mass (Mr)
   • gives abundance of each atom
   • 1. Ionisation chamber
     • beam of electrons fired at atoms
     • Remove 1 electrons from atoms
     • Form +1 ions
       • now can be accelerated
   • 2. Acceleration chamber
     • accelerate towards negative plate
     • Lighter ions move faster than heavier one- relative to Mr
   • 3. drift region
     • Mr relative to speed
     • move towards detector
   • highest m/z = relative atomic mass
     • Low resolution= 1 d.p
   • 4. Detector
     • Ions reach detector at different times
     • produces a current
       • size of current relative to abudance
       • sent to computer
   • relative atomic mass= abundance x mr/ 100
   • High resolution= 5 d.p

3. Ionisation

   • First ionisation energy
     • Energy required for 1 mole of electrons to be removed from 1 mole of gaseous atom to form 1 mole of gaseous positive ions
       • Measured in KJ Mol-1
     • eg Na(g)-- Na+ +e-
   • second ionisation energy eg Na+--Na2+ +e-
   • within element: ionisation energy increases-
   • patterns
     • In atom
       • Increases as neutrons closer to nucleus-more electrostatic attraction
       • Larger increases when move up subunit eg from p to s
       • Large increase between orbitals eg 3s to to 2p
     • In group
       • Decreases as move down group
       • Larger jumps when changing sub orbitals or orbitals
       • Shielding increases
         • Less ectrostatic attraction between nucleus and electron
           • easier to lose electron
     • In period
       • Increases generally but some exceptions
         • Nuclear charge is increases but same shielding
           • more electrostatic attraction
             • harder to lose electron
       • 3rd element
         • move s to p orbital
           • More shielding
       • 6th element
         • electrons starting to double up in the p orbital
           • less stable
             • loses electron easily

4. Isotopes

   • Same no. of protons
   • Different no. of neutrons
   • same chemical properties
     • same no. of electrons in the outer shell
   • same atomic number
   • different molecular mass

5. electron configuration

   • no of electrons in orbital = 2n^2
   • First orbital has 2
   • Rules
     • Fills lowest energy levels first
     • Fill up all boxes singly before doubling up
       • reduce repulsion
     • Arrows go in opposite directions- schrodinger model
     • No more than 2 electrons per orbital
   • Order
     • 1s,2s, 2p, 3s,3p,4s, 3d, 4p,5s,4d..
       • 4s comes before 3d
   • second orbital has 8
   • third has 18
   • If after Ar just put Ar then continue 4s1 ect..
   • orbitals
     • s has max of 2 electrons
     • P has max of 3 so 6
     • D has max 5 so 10
     • F has max 7 so 14
   • Exceptions
     • Copper
       • 1 electron in 4s1 and 1 more in the d orbital
       • More stable
       • With ion
         • 2+ ions
           • lose 1 electrons from s and d orbitals
     • Cr

6. Fundemantals

   • mass
     • Proton
       • Relative 1
       • 1.672x10-27
     • neutron
       • Relative 1
       • 1.672 x10-27
     • electrons
       • 0
       • relative 1/1840
   • charge
     • electrons
       • -1.602x10-19
       • relative -1
     • protons
       • 1.602x10-19
       • realtive +1
     • Neutrons
       • 0
   • Z: atomic number
     • No. protons
   • A: atomic mass
     • No. of protons+neutrons
   • Neutrons+protons: neutrons
     • attracted to electrons to electrostatic attraction
     • attracted together by nuclear force
       • short force
       • prevents protons from repelling each other
   • Relative atomic mass-= average mass of 1 atom /mass of 1 atom of c 12 x 12