Chemistry Topic 1 - Atomic Structure

Chemistry Topic 1 - Atomic Structure

1. Carbon 12

   • Used as a standard for all elements in the periodic table
     • e.g. Hydrogen is 1/12 of Carbon 12 and so it has a Mr of 1

2. Time of Flight Mass Spectrometry

   • Used to determine isotopic masses as well as relative abundance
   • Mass Spectrometer Process
     • 1. Electrospray Ionisation - Sample dissolved in volatile solvent, Hypodermic Needle, High voltage applied, particles gain a proton and become ions
     • 2. Acceleration - Electric Field applied, particles gain the same Kinetic Energy, ions with a lower mass/charge (m/z) ratio experience greater acceleration, usually charge is +1, therefore m/z value is the same as Ar
     • 3. Ion Drift - Ions enter a flight tube, known length, different masses have different ToF, lighter ions reach the detector first
     • 4. Detection - Detector is a negatively charged plate, current produced when ions collide, more ions means bigger current, mass can be calculated from time of flight, abundances can also be calcuated