1) For correct answers of the T1..T5 multiple choice questions it is recommended to calculate the neutron numbers of the nuclei shown in the figures. Number of neutrons = mass number – atomic number (N = A – Z). If the neutron numbers are available, the exercises can be solved easily.

2) For answering the T6 ..T9 multiple choice questions one should remember how the atomic and mass numbers of the decaying nucleus change in the different decay modes.

• In the alpha-decay the atomic number decreases with two, and the mass number with four.
• In the negative beta decay the mass number is constant, but the atomic number increases by one
• In the gamma-decay the mass number and the atomic number remain constant.