A radioactive isotope decays by α emission followed by two β emissions.What is the change in the mass number and atomic number of the original isotope?

Question

Quizplus · Accepted Answer

α emission results in the loss of 2 protons and 2 neutrons from the original isotope, thereby decreasing the mass number by 4. However, the atomic number also decreases by 2 as it loses 2 protons. The subsequent β emissions do not result in any changes in the mass number but increase the atomic number by 1 for each emission. Since there are two β emissions, the total increase in the atomic number is 2. Therefore, the final change in the mass number is -4 and the change in the atomic number is -2+2 = 0, i.e., unchanged. So, the correct option is A, i.e., the mass number decreases by 4 and the atomic number is unchanged.

A Radioactive Isotope Decays by α Emission Followed by Two