Atomic structure
Everything, including us, is made of atoms. Atoms are tiny and have a radius of only 1 × 10-10
metres.
Most of the atom is made of empty space.
The centre of an atom is called the nucleus and this nucleus one ten thousandth (1/10,000) of
the radius of the atom. The nucleus is made of two sub-atomic particles:
• The neutron which has no charge (is neutral).
• The proton which has a positive charge.
Atoms also consist of a third sub-atomic particle which orbit around the nucleus. This particle
is called the electron. The electron is negatively charged.
Usually atoms are neutral (no overall charge) Their number of protons is equal to the number
of electrons.
If an atom loses or gains an electron the charges are no longer balanced and the charged atom
is called an ion. This process is called ionisation.