Higher tier: Ionising radiation
The radiation emitted from unstable nuclei is called ionising radiation because, as it passes through matter, it can dislodge outer electrons from atoms causing them to become ions.
Normally, atoms are neutral.
They have the same number of protons in the nucleus as they have electrons orbiting in the energy levels around the nucleus.
Atoms can, however, lose or gain electrons due to collisions or other interactions, often with nuclear radiation.
When they do, they form charged particles called ions;
- if the atom loses one or more electrons, it becomes a positively-charged ion;
- if the atom gains one or more electrons, it becomes a negatively-charged ion.