Foundation Chemistry

Foundation Chemistry

1. Atomic Structure

   • Fundamental particles
   • Mass spectrometer
     • This is an instrument,or piece of equipment used to analyse the elements in a compound.The process is as it follows:
       • 1) The sample is first vaporized.
         • 2) Ionisation-This is where a beam of electrons from an electron gun are fired at the sample and these electrons knock of electrons from the atom.Usually one electron is knocked off,which forms a charge of 1+.
           • 3) Acceleration- These positive ions are attracted towards negatively charged plates and are accelerated at high speed.The speed they reach depends on their mass.The lighter the ions,the faster they go.Some ions pass through the slits in the plates.This forms the ions into a beam.
             • Deflection-The beam of the ions then moves into a magnetic field at right angles to the direction of travel.The deflection of the ion depends on mass to charge ratio(m/z).Heavier ions are deflected less than lighter ones and 2+ charge ions deflected twice as 1+ ions with the same mass.The deflection also depends on the magnetic field strength.
               • Detection-The magnetic field is gradually increased so that the ions of increasing mass enter one after another.Ions strike the detector,accept electrons,lose their charge and create a current which is proportional to the abundance of each ion.From the strength at which a particular ion hits the detector,the computer works out the value of mass to charge ratio.A read out called mass spectrum is produced.
     • Relative atomic mass is calculated by the sum (relative mass x abundance) divided by the total abundance.
   • Electron arrangement and ionisation energy
   • 1661-Robert Boyle said that substances can't be made any simpler.
     • 1803-John Dalton suggested that elements were made of individual atoms.Atoms can't be broken down.
       • 1896-Henri Bacquerel discovered radioactivity.This showed that particles could come from inside the atom.The same year JJ thompson discovered the electron.He also showed that electron is negatively charged.Thompson alos suggested that electrons were located within the atom in circular rays.
         • 1911-Ernest rutherford and his team found that most of the mass of all the positive charge of the atom was in the tiny nucleus in the centre.
   • Atoms and Electrons
     • 1913-Neil Bohr
       • 1926-Erwin Schrodinger
         • 1932-James Chadwick