Prof.dr Ing. J.F.J van den Brand, Sep. 2006 – 7
| However the
definitive word was given by Mendeleev in 1869 when he arranged the known
elements in a beautiful pattern. Moreover his pattern was predictive in that
some elements were missing with properties that could be predicted. All were
later discovered. |
|
| Thus by the end
of the last century the concept of elements was well developed. The smallest
piece of an element was known as an atom with atoms imagined as small
spheres. |
|
| However 100
years ago the electron was discovered and it became clear that it not only
played an important role in electricity but was also contained inside atoms,
i.e. atoms have sub-structure. |
|