AP BIOLOGY

Detailed explanation-1: -Half-life is the length of time it takes for half of the radioactive atoms of a specific radionuclide to decay. A good rule of thumb is that, after seven half-lives, you will have less than one percent of the original amount of radiation.

Detailed explanation-2: -This rate is known as a half-life; the amount of time it takes for approximately half of the radioactive atoms in a sample to decay into a more stable form. The image above indicates that radium-226 has a half-life of 1, 602 years.

Detailed explanation-3: -The half-life of a radioactive isotope is the amount of time it takes for one-half of the radioactive isotope to decay. The half-life of a specific radioactive isotope is constant; it is unaffected by conditions and is independent of the initial amount of that isotope.

Detailed explanation-4: -Plutonium-239 (a manmade isotope) has a half-life of 24, 000 years.

Detailed explanation-5: -Some radionuclides have half-lives of mere seconds, but others have half-lives of hundreds or millions or billions of years. Two decay chains are shown below: Uranium-238.