Nuclear radiation
Structure of an atom
Inside every The smallest part of an element that can exist. there are even smaller particles: Subatomic particle with a positive charge and a relative mass of 1. The relative charge of a proton is +1., Subatomic particle, with a negative charge and a negligible mass relative to protons and neutrons. and neutrons.
These particles can be found in particular places inside the atom:
Although the word 'atom' comes from the Greek for indivisible, we now know that atoms are not the smallest particles of matter. Atoms are made from smaller subatomic particles.
At the centre of an atom is a nucleus containing protons and neutrons. Electrons are arranged around the nucleus in energy levels or shells.
Both protons and electrons have an electrical charge. Both have the same size of electrical charge, but the proton is positive and the electron negative. The neutron is neutral.
The electrical charge of particles
| Particle | Relative charge |
| proton | +1 |
| neutron | 0 |
| electron | -1 |
| Particle | proton |
|---|---|
| Relative charge | +1 |
| Particle | neutron |
|---|---|
| Relative charge | 0 |
| Particle | electron |
|---|---|
| Relative charge | -1 |
The total number of electrons in an atom is always the same as the number of protons in the nucleus. This means atoms have no overall electrical charge.
