Elements

Elements

1. Are substances which

   • cannot be broken down by chemical means to simpler form
     • Are particles which
       • ATOMS
       • Are the smallest physical units of chemical identity
       • Were initially a philosophical concept
         • Made plausible by
           • Daltons Automic Theory
       • Were shown by Rutherford,s 1911 experiment
         • to be
           • mostly empty space
             • in which
               • negative charge is spread throughout the atomic volume
                 • shown later to contain
                   • ELECTRONS
               • most of the mass is concentrated in a tiny NUCLEUS carrying a possitive charge
                 • charge defines
                   • Atomic numbers
                     • which together characterise a particular
                       • NUCLIDE
                         • nuclides with the same atomic number are known as
                           • ISOTOPES
                             • whose abundances determine the
                 • additional mass due to
                   • NEUTRONS

2. which number

   • 92 in Nature

3. characterised by experimentaly observed

   • Distinctive Properties
   • Abundance Profiles
   • Relative Masses (Atomic Weights)
     • leading to
       • Atomic weight scale
         • whose units are
           • Unified Atomic Mass Units
   • Isotopic Composition
     • as observed by
       • Mass Spectrometry