When the two atoms bind to form NaCl, sodium shares its single outer electron with chloride, and so, both are stable. In ordinary chemical reactions, such as the binding of Na to Cl, electrons that are lost or gained are always those on the outermost orbit. These charged atoms are called ions, and they are stable in water despite their electrical charges. What differs from an ordinary chemical reaction is that when radiation donates energy to atoms or molecules, electrons other than those on the most outer orbit can be released, which makes the atoms very unstable. Such unstable atoms are called radicals and are chemically very reactive.
Some radicals are so reactive that they exist only for as short a time as a microsecond.
X and gamma rays differ from beta particles in that they release high-speed electrons from atoms first. Positively charged particles transfer energy to molecules in cells by essentially the same mechanisms. Neutrons are somewhat different since they are electrically uncharged, and their main effect is to impact the nuclei of hydrogen atoms, namely protons. Since the masses of a neutron and a proton are similar, the impact results in an elastic scattering process like in billiards. The ejected protons behave as charged particles.