Introduction

All the things have certain energetic stage or level of static energy. They always want to find the lowest energetic stage, which is called basic stage and it is stage of highest stability. In the most of cases this includes recombination done by adding or loosing item and in all cases it leads to release extra energy - in big amounts if particles are atoms, and in huge amounts if particles are nuclei. If bonding energy of atom or nuclei increase, the stability increases too, it means that its chance to change is lower. Bonding energy ( Ev ) - added amount of energy needed to split given atom or nucleus to its items. Static energy of atom or nucleus is lower than whole static energy of its particles when they are alone. It happens because when particles are together they are in lower energetic state so they have lower energy. Bonding energy is the scale of this difference of potential energies - it is energy needed "to come back by other way" - how much it is bigger, the potential energy of atom or nucleus is lower, and their stability is bigger. Bonding energy depends on atom and nucleus.

Nuclear power
Nuclear power is strong attractive force, which holds parts of nucleus (nucleons) together and overcome electric power between protons. Its influence depends on the greatness of nucleus, because force occurs only between neighbouring nucleons. If attractive effect of nuclear power is greater, the bonding energy is also bigger (it means that more energy was released when particles have joined).

Radioactivity
Radioactivity is property of some unstable nuclei, which are spontaneous changing themselves to nuclei of other elements and emits radiation, process is known as radioactive decay. We know 3 types of radiation emitted by radioactive elements - flow of  particles (called  rays), flow of  particles ( rays) and  rays.
Radioisotope (radioactive isotope) - whatever radioactive substance (all substances are isotopes). The most of them exist always, because they have very long half-life (e.g.: uranium-238), however one, carbon-14, is still produced by cosmic radiation (background of radiation). Other radioisotopes are produced splitting of nuclei and even more are produced in research centres, where very fast particles (from protons up to uranium nuclei) hit them. They are speeded by stimulants of particles (e.g.: cyclotrons).
 particles
Positive charged particles got from some radioactive nuclei ( decay). They are quite heavy (2 protons + 2 neutrons), they move quite slowly and have small penetrating power.
Penetration: several cm of air, thick sheet of paper