Lesson 12: Understanding Radiation Measurements

Radiation and Measurements

Radiation is the transmission of energy through space, including heat, light, radio waves, x-rays, and many other forms of energy. Atomic radiation, not unexpectedly, is the transference of energy between atoms, which are composed of particles held together by electrical and nuclear forces.

Ionizing Radiation

In some cases, an atom can receive a form of radiation, such as heat, and pass it along to the next atom without the energy altering the protons, neutrons, and electrons that form the structure of an atom. In other cases, the radiation does alter the atomic structure, leaving the atom in a state which scientists call unstable. In an effort to return to a stable state, the nucleus of the atom becomes radioactive and begins radioactive decay, meaning that it sends out particles or waves of energy that will then render other atoms unstable. This "destabilizing" radiation, called ionizing radiation, strips electrons from their orbits around an atom's nucleus, disrupting the positive and negative electrical charges which hold an atom together. The changes in these charges then alter the chemical properties of the atom.
Atoms have a set number of protons and electrons that are used to describe their chemical properties, but one chemical element can have a variety of isotopes, which are simply forms of the same chemical element with the same number of protons but with varying numbers of neutrons. The number of protons (and electrons) in the atom helps to determine the chemical properties of the element, but the number of neutrons influences the ability of the atom's nucleus to remain stable. As a result, the ratio of neutrons to protons identifies the nuclear, potentially radioactive properties of the atom. An isotope which emits radioactive energy to regain stability is called a radionuclide.

Some radioactive atoms and radionuclides can decay--emit energy to return to a stable condition--in a matter of minutes. Others must decay for thousands, even billions, of years before regaining a stable state. To measure the rate of an atom's decay process, scientists use a formula to calculate radioactive half-life, which is the time required for one-half of a radioactive material to undergo radioactive decay. After seven half-lives, the level of radioactivity will be less than 1% of the original radioactivity. In part, however, the actual time needed for a radioactive material to decay will depend on what type of radiation it emits.

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