The Structure of the Atom

Atoms are actually made from even smaller particles. There are three types of particle in an atom:

• protons

• neutrons

• electrons

How these particles are arranged in an atom is illustrated below:

These particles occupy special positions inside the atom and have their own properties.

The protons and neutrons are at the centre of the atom in the nucleus. The nucleus forms a very small part of the size of an atom.

The electrons orbit the nucleus in layers called shells.

Protons and neutrons both have a mass of one atomic mass unit (amu) and electrons have almost no mass (0 amu).

Protons are positively charge (1+), neutrons have no charge and electrons are negatively charged (1-).

Next section: Atomic number and mass number