In the world of nuclear physics, there are numerous methods of radioactive decay which an element can undergo. Each of these has different implications for the element and its surroundings. These different types of decay can explain why multiple instances of the same element or ion can decay into drastically different waste materials.
The first type of radioactive decay is known as alpha decay. It is named for the fact that in the process of decay, each atom emits an alpha particle from its nucleus. These alpha particles are very similar in nature to a helium nucleus, containing 2 protons, no electrons, and having an atomic mass number of 4. In order to determine what might be the product of alpha decay, there is a simple formula we can use. Recall that an element can be written as its symbol with the atomic mass number to the left in superscript, and the atomic number (number of protons) on the left in subscript. By using this notation, we can use basic mathematics to determine the product.
Simply write the original element in the above notation, followed by a right-pointing arrow, and then the produced elements. One of them will be an alpha particle, and then the other particle will have atomic mass number and proton count equal to the original values minus the respective values of the alpha particle. Thus, if Uranium-235 undergoes alpha decay, a Thallium atom with 90 protons and an atomic mass number of 234, in addition to the alpha particle.
The second type of decay is known as beta-minus decay. Rather than an alpha particle being emitted, only a single electron will be emitted. Consider the decay of carbon-14, which is commonly used in radioactive dating. We use the same method as before, except assigning an atomic mass number of 0 and an atomic number of -1. This tells us that the resulting atom will be a Nitrogen atom with 7 protons and the same atomic mass number of 14.
The final type of radioactive decay is beta-plus decay. Instead of an electron emitted, a positron is emitted. This is the same as the above electron except with a proton count of +1. Consider sodium-22, which decays into an isotope of neon-22 through the emission of a positron.
The concept of radioactive decay is one of the most powerful and widespread phenomena in the world of physics, and is essential to much of our historical knowledge.