The periodic table is a tabular display of the chemical elements, organized on the basis of their properties. Elements with similar properties together, such as the halogens and the noble gases. These gaps form four distinct rectangular areas or blocks. The f-block is not included in the main table, but rather is usually floated below, as an inline f-block would make the table impractically wide. The periodic table accurately predicts the properties of various elements and the relations between properties. As a result, it provides a useful framework for analyzing chemical behavior, and is widely used in chemistry and other sciences.