"I consider it well to observe that no law of nature, however general, has been established at once..."
The Periodic Table is arranged such that elements with similar properties are allocated together. Arrangements are based on the periodic nature of the elements, a property that allows certain properties of elements repeat periodically as a function of atomic mass. The periodic table is subdivided into four blocks: the s, p, d and f blocks. These blocks are indicative of the valence electron configuration of the atom. The outer shell of the s block elements consists of elements with valence electrons in s atomic orbitals. Similarly, outer shell of p, d and f block elements consist of elements with valence electrons in p, d and f atomic orbitals respectively.
The periodic table consists of vertical groups and horizontal periods. Elements in a vertical group
typically have the same number of electrons in their outermost shell. Thus, elements in a group exhibit similar reactive properties.
Elements in horizontal periods have the same principal quantam, n, indicating the number of electron shells in the atom.