2. Which of the following is the best definition of half-life for a radioactive substance? O A. Half of the amount of time required for all of the radioactive atoms to decay.
O B. The amount of time required for half of the radioactive atoms to decay.
O C. The amount of time required for each radioactive atom to decay halfway.
O D. All of the above.

The amount of time required for each radioactive atom to decay halfway.

Explanation:

In radioactivity, which is the spontaneous emission of radiations from the nucleus of an unstable atom, each atom has a specific term called HALF-LIFE and is denoted by t1⁄2. Half-Life of an atom represents the amount of time it takes the nucleus of that atom to decay by half.

Therefore, based on the definitions given in the question, "The amount of time required for each radioactive atom to decay halfway" best describes HALF-LIFE.

- The first definition is wrong because it is NOT HALF THE AMOUNT OF TIME but half the amount of the atom while the second definition is wrong because it is NOT ALL THE ATOMS but a specific atom. Each atom has its own specific half-life.