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Nuclides are atoms with a specific number of protons and neutrons, which can be stable or unstable. There are approximately 1,700 known nuclides, 1,400 of which are radioactive. Isotopes are sets of the same element with different numbers of neutrons. Unstable nuclides emit alpha or beta particles or gamma rays and eventually decay into stable nuclides. Nuclear power plants use nuclides for energy through fission, which breaks heavier nuclides into lighter ones.
Nuclides are atoms with a certain number of protons and neutrons. Usually an isotope of an element, they can be stable or unstable. Unstable nuclides are radioactive. There are approximately 1,700 known nuclides, 1,400 of which are radioactive.
The terms “nuclide” and “isotope” are sometimes used interchangeably, but are not synonymous. Isotopes are sets of the same element that have different numbers of neutrons. Isotopes are nuclides, but nuclides are not necessarily isotopes.
Elements are defined by the number of protons they possess. The periodic table of elements is organized by the number of protons in each element. Every element in the periodic table is a nuclide, as are all isotopes of each element.
The scientific notion for a nuclide is usually written AZX. The X stands for the symbol of the element, the Z for the number of protons, or atomic number, and the A stands for the mass number, or the number of protons plus neutrons in the element. For example, the notion of lithium is written 73Li. This tells us that lithium contains three protons and four neutrons, since 7 minus 3 is 4. Lithium also has several isotopes, such as 63L, written as lithium-6. Lithium-6 contains only three neutrons.
Protons naturally repel each other because they all carry a positive charge, so the stabilizing influence of neutrons is what keeps an element intact. If the nuclide is light, it is usually stable when the number of protons and neutrons is equal or nearly equal. The heavier the element, the higher the neutron to proton ratio needed to make it stable.
Unstable nuclides are radioactive and occur naturally or are artificially produced. There are three types of radiation emitted by an unstable nuclide: alpha or beta particles or gamma rays. Alpha and beta particles are harmless enough because you can easily prevent them from entering your body. Gamma rays, however, are extremely harmful which is why radioactive elements are considered so dangerous. The breakdown of an unstable nuclide is called radioactive decay.
An unstable nuclide eventually decays into a stable nuclide. Each radioactive nuclide has a fixed rate of decay, known as its half-life. Knowing the half-life of certain elements and measuring the ratios of stable to unstable nuclides in a given object allows scientists to date fossils and artifacts.
Nuclear power plants also use nuclides to create energy through a process called fission. Occurs in a nuclear reactor, fission breaks heavier nuclides into lighter ones. This reaction releases energy which is harnessed by the plant. Nuclear power is often considered dangerous because the nuclide used in the fission process, uranium-235, is a radioactive isotope.
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