ATOMIC STRUCTURE

• Define mass number of an atom

  Number of protons and neutrons in the nucleus of the atom.
• Relative atomic mass


  Average mass of an atom compared to C-12 on a scale in which an atom of C-12 is exactly 12.
• 6.022 x 10^23


  To find 1
• Two reasons why it is necessary to ionise the isotopes

  Acceleration and Current at detector.
• Zinc isn’t a transition metal
• Electronspray Ionisation 


  Sample is dissolved in volatile solvent.

  Injected through nozzle at high voltage.

  Each molecule gains H+
• Electron configuration for Cr

  (Ar) 3d5 4s1
• Electron configuration for Cu

  (Ar) 3d10 4s1
• Do chemical properties of isotopes differ?

  No, same electron configuration.
• How are ions formed in TOF?

  Sample bombarded by high energy electrons, the sample molecule loses an electron forming M+.
• TOF is able to separate two species to give two peaks

  Positive ions are accelerated by an electric field.

  To constant acceleration.

  The positive ions with m/z of 104 have the same kinetic energy as those with 118 and move faster.

  Ions with m/z of 104 arrive at detector first.