What is radioactivity?
Radioactivity is the spontaneous emission of energy from unstable atoms. Atoms are found in all natural matter. There are stable atoms, which remain the same forever, and unstable atoms, which break down or ‘decay’ into new atoms. These unstable atoms are said to be ‘radioactive’, because they emit radioactivity from the nucleus as they decay. Radioactive elements, such as uranium, thorium and potassium break down (decay) fairly readily to form lighter atoms. The energy that is released in the process is made up of small, fast-moving particles and high-energy waves. These particles and waves are, of course, invisible. (The level of radioactivity of an element varies according to how stable its atoms are). Other elements with naturally occurring radioactive forms, (isotopes) are carbon, bismuth, radon, and strontium. Radioactivity is a random process that happens naturally as the isotopes in particular elements decay. The isotopes continue to break down over time. The length of time tha
Radioactivity is the process by which unstable elements become more stable by emitting particles and energy. This process is measured in “half-lives,” the time it takes half of a radioactive material to decay into a more stable element. The half-life of plutonium-239 is 24,000 years; that of uranium-235 is 704 million years.
Radioactivity is the process whereby unstable atomic nuclei release energetic subatomic particles. The word radioactivity is also used to refer to the subatomic particles themselves. This phenomenon is observed in the heavy elements, like uranium, and unstable isotopes, like carbon-14. Radioactivity was first discovered in 1896 by the French scientist Henri Becquerel, after which the SI unit for radiation, the Becquerel, is named. Becquerel discovered that uranium salts were able to blacken a photographic plate placed in the dark, even through a paper barrier. Subsequent experiments distinguished three distinct types of radiation — alpha particles, beta particles, and gamma rays. These are positively charged, negatively charged, and neutral, respectively. In the United States, human exposure to radioactivity is measured in rads, where one rad represents 0.01 joule of energy absorbed per kilogram of tissue. Radioactivity is a random process, meaning that it is physically impossible to
Radioactivity is the emission of energetic particles or waves from atoms. Natural radiation occurs when unstable nuclei transform to some other nucleus by emitting radiation. Induced radiation often occurs when electrons which have been excited lose energy in the form of X-rays or microwaves, as done in dentist offices, microwave ovens, and radar. As it applies to nuclear energy, many materials created during the operation of a reactor are unstable. As they decay over varying lengths of time (from microseconds to hundreds of thousands of years), they emit energetic particles or waves.
