Click on the animation to see the sub atomic particles.
Imagine you have a piece of aluminium foil which is used in cooking
etc. If you cut the sheet in two each sheet is still made of aluminium.
Imagine you continue splitting the aluminium foil into smaller and smaller
pieces , what will you eventually have? Even a small piece of aluminium
contains millions of atoms because atoms are so small millions would fit
on a pinhead.
Sometimes substances are made from more than one atom. If you tried to get the smallest drop of water you would not find a single atom , instead you would find a group of atoms joined together and this group is known as a molecule.
In the case of water the group or molecule is made up of 2 Hydrogen
atoms and 1
Oxygen
atom and this gives us
the chemical formula
H2O.
So how does the two atoms join together to form a molecule of water?
To answer this question we must look closer at the original building block that is the atom and what an atom is made up of.
Experiments carried out in the early 1900's showed that an atom was made up of smaller building blocks called sub atomic particles. These particles are called protons, neutrons and electrons.
Click on the animation to see the sub atomic particles.
It was once thought that the particles were all bundled up together in the atom but in 1911 Rutherford showed that this was not the case. He showed that the atom was mostly empty space and that all the protons and neutrons were gathered together at the centre of the atom to form the nucleus and that the electrons circle the nucleus at high speed thus creating a blur or cloud around the nucleus similar to the effect of a fast moving propeller on an aeroplane.
Table 1 sums up the differences between the sub atomic particles.
TABLE 1
| Particle | Mass | Charge | Location |
| Proton | 1 | Positive | In the nucleus |
| Neutron | 1 | Neutral | In the nucleus |
| Electron | 1 /1840 | Negative | Circling the nucleus at high speed |
The nature of the atom is determined by the number of protons in
its nucleus and by the number of electrons circling the nucleus. If an
atom has more electrons than protons it will be
.............. charged and vice versa. This type of atom is known as
an ion.
An element is made up of only type of atom. There are 106 different elements so how can one atom be different to another?
The answer lies in the number and arrangement of these sub atomic particles.
As we have noted there are 106 different elements all of which have different numbers of sub atomic particles all these different elements have been placed in a special table called the periodic table of the elements. In this table all the elements have a different symbol denoted by letters and the elements are listed in order according to the number of protons in the nucleus of an atom of the element. This is known as the atomic number of the element. For example the first element in the table is Hydrogen which has the symbol "H" and has 1 proton in its nucleus of its atom. Click here to see my interactive Periodic Table
How many protons in the nucleus of Calcium which is number 20 in the periodic table?
Now that we are familiar with the basic building block, the atom we can move on to how atoms bond together.
