Periodic table: number of elements per block

The elements of the periodic table can be categorized in a variety of ways. For display purposes, an 18 column table is generally used, with seven rows across, and this corresponds with the number of electrons in the outer rings of each atom. Thereafter, the elements are often color-coded to separate them into blocks and chemical groups, which corresponds more with their chemical properties and characteristics.

In most cases the table is split into four blocks, with ten separate groups. "s-block" (sharp) is displayed on the left of the table and includes alkali metals and alkaline earth metals, as well as hydrogen (a nonmetal) and helium (a noble gas, usually displayed on the right). In the center of the table is usually "d-block" (diffuse), which is the largest individual group and is comprised of the transition metals. "p-block" (principal) is the most diverse, it includes five separate groups and is found on the right of the table. Finally, "f-block" (fundamental) is the lanthanides and actinides, which are generally not considered to follow the sequence shown in the 18 column table, and are usually displayed separately and below the table (although they are sometimes put in sequence in a 32 column table as part of the 6^th and 7^th rows).