Atomic Structure


Fundamental particles

  • Nucleus of atom contains protons and neutrons
  • Electrons surround nucleus in orbitals
  • Relative masses:
    • Proton- 1
    • Neutron- 1
    • Electron- 1/1840
  • Relative charges:
    • Proton- +1
    • Neutron- 0
    • Electron- -1

Mass number and isotopes

  • Atomic number (Z)- number of protons in nucleus of atom
  • Mass number (A)- total number of protons and neutrons in nucleus of atom
  • Isotopes- atoms with the same number of protons but different numbers of neutrons
    • Same chemical properties- same electron configuration
  • TOF Mass Spectrometer
    • High vacuum- prevents ions produced from colliding with particles in air
    • Electrospray ionisation: 
      • Sample dissolved in volatile solvent
      • Forced through fine hollow needle connected to positive terminal of high voltage supply
      • Produces tiny positively charged droplets- gained proton from solvent
      • Solvent evaporates, leaving single positive ions
    • Electron impact:
      • Sample vaporised
      • High energy electrons fired at it from electron gun
      • Electron gun: hot wire filament with current running through it…


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