Nuclear chemistry is the study of changes of the nucleus of an atom. The nucleus contains protons and neutrons, together known as nucleons. A nucleus has a lower mass than the sum of the masses of the nucleons that form it. The difference in these masses is termed the mass defect and is equivalent to an amount of energy according to Einstein's mass–energy equivalence. Nuclei are more stable at certain neutron-to-proton ratios. Unstable nuclei break down into more stable nuclei through radioactive decay. During radioactive decay, new nuclei form naturally via transmutation. Elements that are heavier than those that occur naturally can be formed via artificially induced transmutation. Nuclear fusion and nuclear fission represent two types of nuclear reactions. In fusion, small nuclei fuse together to form a larger nucleus. In fission, a large nucleus splits into smaller nuclei. Both fusion and fission can potentially release energy. Current nuclear technology uses nuclear fission to produce electricity.
At A Glance
- Nuclear chemistry is the study of changes in the nuclei of atoms. A nucleus consists of two types of nucleons—protons and neutrons—that are held together by the strong nuclear force.
- Nucleons in a nucleus have lower energy than nucleons outside of a nucleus, resulting in a mass defect. Einstein's mass–energy equivalence relates mass and energy.
- Nuclei are most stable when their neutron-to-proton ratio is close to one. When the neutron number versus proton number is graphed for all known isotopes, a zone of stable isotopes is at the center.
- Unstable nuclei break down into smaller nuclei over time by radioactivity.
- Nuclides change to form one or more new nuclides in a nuclear reaction. In a balanced nuclear equation, proton and neutron numbers are balanced.
Nuclides can be synthesized artificially. The conversion of one nuclide into another nuclide is called transmutation.
Nuclear fission is the process by which a nuclide splits into two or more smaller nuclides, and nuclear fusion is the process in which two or more nuclides combine to form a larger nuclide.
- A chain reaction is a nuclear reaction in which the products of the reaction can trigger more nuclear reactions. An uncontrolled chain reaction will cause a fissile material to undergo nuclear reaction very quickly.
- A nuclear reactor uses a nuclear reaction at a controlled rate to generate heat that is converted to produce electricity.