A fundamental particle
cannot be broken down into anything simpler.
The Greeks philosophised
that if you take an object and break it into two pieces, then take one
of the halves and halve that and so on.. you would eventually get to a
point where the object would not divide any further (Greek - atom (indivisible)).
It was thought that
each substance had its own fundamental particle. The universe could then
be thought of as composed of millions of different 'matter building bricks'!
One for water one for salt, one for gold, one for grass etc.. We now know
that substances such as gold are made up of atoms but substances such
as water are made up of individual units called molecules that
it is possible to break down into smaller components - atoms. Grass is
living matter. It is made up of complex and simple molecules associated
into vast biological units called cells... but all of these could be broken
down into atoms too. The atoms matter is made up of is listed in the Periodic
Table. We therefore have a set of just over 90 'matter building bricks'
that all of the matter in the universe could be considered to be made
of!
By the end of your
GCSE you were aware of the fact that atoms can be thought of as composed
of protons, neutrons and electrons. The number of protons in the
nucleus determining which atom we are dealing with, the number of neutrons
telling us which isotope of that atom and the number of electrons
orbiting the atom determining whether the atom was indeed a neutral atom
or an ion. Our 'matter building brick' set is now much simpler.. from
only three different types of 'brick' we could make anything - a Lego
set for God!
The simplicity of this
has a sort of beauty. it feels 'right'.. it is an elegant picture of matter.
a pleasing model.
BUT we now know this
is not the solution to the fundamental particle puzzle..although electrons
have not yet been broken down into anything simpler, protons and neutrons
can be broken down into quarks.
The Standard Model
This is the currently held view of matter - but it is
being disputed and refined and at University level you will learn of
its limitations and the suggestions as to how it should be amended -
Remember we only have a 'model' of how things work - NOT the absolute
truth - we seek to get a clearer picture, a better understanding of
how the Universe works!
(For
the latest interactive version of this click on the image and go to particle
adventure!)
Hadrons and Leptons
We now have two sets
of sub-atomic particles:
hadrons
(from the Greek meaning 'massive' or 'bulky' - heavy ones) that are
made up of quarks and