Atoms and radiation
... explains radiation, where it comes from, how
it differs from radioactivity, and its different types.
All matter in the world about us consists of atoms. These are the basic building blocks of the elements such as hydrogen, carbon, oxygen, iron, and lead.
Each atom contains a tiny central positively charged nucleus and a number of electrons.
The electrons carry negative electric charge and move around the nucleus in clouds — or shells as they are called — with loosely defined boundaries. The nucleus is typically 10 000 times smaller than the electron clouds and the electrons themselves are even smaller.
This means that the atom is mainly empty and difficult to depict except in diagrams, which are largely schematic.