Hypothetical elements are theoretical substances that do not exist in reality but are proposed based on scientific principles or predictions. They are often used in discussions about chemistry and physics to explore possibilities beyond known elements. For example, scientists might theorize about elements that could exist under extreme conditions, such as those found in the cores of stars or in other galaxies. These elements can help researchers understand the behavior of matter and the fundamental forces of nature. By studying hypothetical elements, scientists can refine their theories and models, leading to new discoveries in fields like quantum mechanics and astrophysics.