Radioactivity Study Guide

When an unstable atomic nucleus undergoes radioactive decay (alpha or beta decay), it transforms into a different nucleus. However, this newly formed nucleus is often left in an excited or high-energy state. To transition to a more stable, lower-energy configuration, the nucleus rearranges its internal structure. This nuclear rearrangement releases the excess energy in the form of electromagnetic radiation known as gamma rays. Gamma rays are high-energy photons, and their emission does not change the atomic number or mass number of the nucleus; it merely lowers the energy state of the nucleus. This process often follows alpha or beta decay, making gamma emission a common feature of many radioactive decay sequences.

Nuclear equations represent changes that occur within the nuclei of atoms during processes like radioactive decay or nuclear reactions. Unlike chemical equations which conserve atoms, nuclear equations conserve both mass number (the total number of protons and neutrons) and atomic number (the total number of protons, which represents charge). To balance a nuclear equation, you must ensure that the sum of the mass numbers on the left side of the equation equals the sum of the mass numbers on the right side. Similarly, the sum of the atomic numbers on the left must equal the sum of the atomic numbers on the right. This conservation allows for the identification of unknown particles or isotopes produced or consumed in a nuclear reaction. For example, in alpha decay, a helium nucleus (two protons, two neutrons) is emitted, leading to a decrease of 4 in the mass number and 2 in the atomic number of the parent nucleus.