Types of radiation
(examples, body, used, process, plants, form, energy, carbon, cause, basic, change, Stable and unstable nuclei, Types of radiation
The forms of radiation most commonly emitted by a radioactive nucleus are called alpha particles, beta particles, and gamma rays. An alpha particle is the nucleus of a helium atom. It consists of two protons and two neutrons. Consider the case of a radium-226 atom. The nucleus of a radium-226 atom consists of 88 protons and 138 neutrons. If that nucleus gives off an alpha particle, it must lose the two protons and two neutrons of which the alpha particle is made. After emission of the alpha particle, the remaining nucleus contains only 86 protons (88 − 2) and 136 neutrons (138 − 2). This nucleus is the nucleus of a radon atom, not a radium atom. By emitting an alpha particle, the radium-226 atom has changed into an atom of radon.
The emission of beta particles from nuclei was a source of confusion for scientists for many years. A beta particle is an electron. The problem is that electrons do not exist in the nuclei of atoms. They can be found outside the nucleus but not within it. How is it possible, then, for an unstable nucleus to give off a beta particle (electron)?
The answer is that the beta particle is produced when a neutron inside the atomic nucleus breaks apart to form a proton and an electron:
neutron → proton + electron
Recall that a proton carries a single positive charge and the electron a single negative charge. That means that a neutron, which carries no electrical charge at all, can break apart to form two new particles (a proton and an electron) whose electrical charges add up to make zero.
Think back to the example of carbon-14, mentioned earlier. A carbon-14 nucleus decays by giving off a beta particle. That means that one neutron in the carbon-14 nucleus breaks apart to form a proton and an electron. The electron is given off as a beta ray, and the proton remains behind in the nucleus. The new nucleus contains seven protons (its original six plus one new proton) and seven neutrons (its original eight reduced by the breakdown of one).
The loss of an alpha particle or a beta particle from an unstable nucleus is often accompanied by the loss of a gamma ray. A gamma ray is a form of high-energy radiation. It is similar to an X ray but of somewhat greater energy. Some unstable nuclei can decay by the emission of gamma rays only. When they have lost the energy carried away by the gamma rays, they become stable.