The electron is a subatomic particle that has negligible mass and is negatively charged. The properties of X-rays and their interaction with matter concern the orbiting electrons with the atom.
Electrons orbit the central positively charged nucleus in shells, the outermost one of which is termed the valence shell.
- Farr's Physics for Medical Imaging (2nd edition): ISBN 0702028441
- Physics for diagnostic radiology (Dendy, Heaton): ISBN 0750305916