Elements

Annotations:

• Elements

1. Are substances which
   1. cannot be broken down by chemical means to simpler form
      1. Are particles which
         1. ATOMS
         2. Are the smallest physical units of chemical identity
         3. Were initially a philosophical concept
            1. Made plausible by
               1. Daltons Automic Theory
         4. Were shown by Rutherford,s 1911 experiment
            1. to be
               1. mostly empty space
                  1. in which
                     1. negative charge is spread throughout the atomic volume
                        1. shown later to contain
                           1. ELECTRONS
                     2. most of the mass is concentrated in a tiny NUCLEUS carrying a possitive charge
                        1. charge defines
                           1. Atomic numbers
                              1. which together characterise a particular
                                 1. NUCLIDE
                                    1. nuclides with the same atomic number are known as
                                       1. ISOTOPES
                                          1. whose abundances determine the
                        2. additional mass due to
                           1. NEUTRONS
2. which number
   1. 92 in Nature
3. characterised by experimentaly observed
   1. Distinctive Properties
   2. Abundance Profiles
   3. Relative Masses (Atomic Weights)
      1. leading to
         1. Atomic weight scale
            1. whose units are
               1. Unified Atomic Mass Units
   4. Isotopic Composition
      1. as observed by
         1. Mass Spectrometry