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

the neutrons in the nuclei

its beta particles

the nuclei in a sample

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:

where, n = order of the reaction

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

21 stacks

step-by-step explanation:

divide 630/30

21 stacks

enjoy!

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.