atomic structure

• Sub-Atomic Particles


  The fundamental particles; protons, neutrons and electrons
• Nucleus


  The central part of the atom containing protons and neutrons
• Nucleons


  The sub-atomic particles within the nucleus
• Proton


  A sub-atomic particle:

  - Relative mass = 1

  - Relative charge = +1

  Contained within the nucleus

  
• Neutron


  A sub-atomic particle:

  - Relative mass = 1

  - Relative charge = 0

  Contained within the nucleus

  
• Electron


  A sub-atomic particle:

  - Relative mass = 1/1840

  - Relative charge = -1

  Surrounds the nucleus in orbitals
• Electrostatic Force


  The force that holds protons and electrons together in the atom
• Isotope


  The same number of protons within the nucleus, the same number of electrons, but a varied number of neutrons within the nucleus. The element does not change and is chemically the same due to the same number of electrons interacting with other electrons and elements

  
• Mass Number


  Number of protons + number of neutrons.

  Also known as nucleon number (Physics)

  
• Atomic Number


  Number of protons.

  Also known as proton number

  
• Time of Flight Mass Spectrometer

  A device that measures the abundance of isotopes in a sample
• TOF:MS


  Abbreviation for time of flight mass spectrometer
• Vacuum


  The whole TOF:MS is kept under this condition to prevent interference of foreign particles
• Ionisation


  The sample is dissolved in a volatile solvent and pushed through a fine hollow point needle. This needle is connected to a positive high voltage supply, which rips off electrons from the sample. The solvent then evaporates to form single ions
• Acceleration


  The positive ions are attracted towards a negative plate. Lighter ions travel faster
• Ion Drift


  The ions pass through a hole in the negatively charged plate. This forms a bean of ions which travel across a flight chamber
• Detection


  When ions meet the detector (at different velocities due to their varies masses) the flight times are recorded as they hit a detector which causes a flow of current. This current enables the machine to identify how abundant that mass is
• Data Analysis


  The signal that is detected is sent to a computer which plots on a graph the abundance of that mass
• Low Resolution


  A TOF:MS that detects to one decimal place. This is a more common TOF:MS
• High Resolution


  A TOF:MS that detects to five decimal places. This is a less common TOF:MS
• Mass/Charge Ratio


  What data is plotted from a TOF:MS
• Overall Isotope Present


  [(m/z1 x abundance1) + (m/z2 x abundance2)...]

  / total abundance
• Mini-Mass Spectrometer


  A mass spectrometer that investigates a library of spectra to detect chemical weapons, drugs or explosives
• s


  The first sub-level, can hold 2 electrons
• p


  The second sub-level, can hold 6 electrons
• d


  The third sub-level, can hold 10 electrons
• f


  The fourth sub-level, can hold 14 electrons
• Ionisation Energy


  The minimum enthalpy change required to remove one mole of electrons from one mole of an element in the gaseous state