Where does ionizing radiation come from?
An atom is made up of a nucleus containing protons (positively charged) and neutrons (have binding energy though no electrical charge). Both represent more than 99,9 per cent of the atom's weight and determine the properties of the element.
Revolving in orbit around this nucleus, there are electrons, negatively charged.
A stable atom has equal number of protons and electrons. When an atom has an imbalance between protons and electrons it is considered unstable, or radioactive. Unstable atoms are called radioisotopes or radionuclides. Ionizing radiation comes from an instability in the atom.
In the process of achieving stability a part of the nucleus of a radioisotope disintegrates and emits particles and energy, until it reaches stable equilibrium. Hence radioactive elements do emit particles and energy until they transform into stable and lighter elements at the end of their decay chain.
The half-life of a radioactive element represents the time it takes for one half of any quantity of it to decay into the next lighter element along its decay chain. A complete radioactive decay often takes very long periods of time. For instance, uranium 238 takes about twenty-eight billion years for half of it to decay into a stable form of lead.
Ionizing radiation occurs when it has enough energy to remove one or more electrons from an atom with which it comes in contact. Thus, the ionized atom is made chemically reactive and capable of damaging living tissue.
Nonionizing radiation -as in the form of microwaves- occurs when it does not have sufficient energy to remove electrons from atoms. It can also, however, be damaging to human health.