A Level Physics Practice Exam 2026 – The All-in-One Guide to Mastering Your Physics Exam!

Ionisation involves the process where an electron is removed from a neutral atom. When an atom is neutral, it has an equal number of protons and electrons. By removing an electron, the balance of charge is disrupted, resulting in a positively charged ion, also known as a cation. This process requires energy to overcome the electrostatic attraction between the negatively charged electron and the positively charged nucleus.

In contrast, adding an electron would lead to the formation of a negatively charged ion, not ionisation. Removing a proton or a neutron does not fall under the definition of ionisation; protons are responsible for the identity of the element, and neutrons affect the isotope but not its charge. Therefore, the correct understanding of ionisation is centered on the removal of an electron from a neutral atom.