Question

A half-life of a radioactive substance is the amount of time needed for one half of _____ to decay into a stable isotope.

Answer 1

Answer:

its the nuclei in a sample

Explanation:

Answer 2

Answer: The correct answer is the nuclei in a sample.

Explanation:

Half life is defined as the time taken for half of the reaction to complete. This is also defined as the time in which the concentration of a reactant is reduced to half of its original value.

General expression for half life period of a reaction for nth order is: $t_{1/2}=\frac{1}{[A_0]^{n-1}}$

where, n = order of the reaction

Hence, the correct answer is the nuclei in a sample.