Radioactivity

Radioactivity is a property of element isotopes and heavy elements, such as radium, uranium, and plutonium. The atomic nuclei of these substances are unstable, so they decay by various means into more stable configurations. The three most common forms of radioactivity are alpha particles, beta particles, and gamma rays. Large doses of radiation can be quite harmful, so care must be used in handling radioactive materials.

Alpha particles are helium nuclei, which are typically emitted by heavy nuclei, such as uranium. Alpha particles have a very short range - most can be stopped by a thin sheet of paper or foil. Nevertheless, they can be quite harmful, especially when in contact with skin. When an element undergoes alpha decay, it turns into a new element with atomic number two less and atomic weight decreased by 4.

Beta particles are energetic electrons, which are emitted by neutrons in neutron-rich nuclei. When an atom undergoes beta decay, a neutron is converted into a proton, increasing the atomic number by 1, and an electron and an antineutrino, an extremely light and almost undetectable particle, are emitted. Beta particles are more penetrating than alpha particles but not as dangerous.

Gamma rays are not particles of matter but energetic photons, particles of electromagnetic radiation. They are emitted by excited nuclei, which are in turn the products of previous radioactive decay. Gamma rays are more penetrating than alpha or beta particles. They are typically able to pass through several centimeters of lead.

There are other more exotic forms of radioactivity as well, such as positron emission, electron capture, neutron emission, and spontaneous fission.

Radioactivity can be a useful scientific tool when used properly. For instance, PET scans, which scan the inside of the human body, rely on positron emission. Also, radiation treatment is used in chemotherapy and radioactive elements are often used as tracers in medicine. Radioactive carbon dating is used to determine the age of ancient artifacts.

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