How is the periodic table arranged?

The periodic table is organized by increasing atomic number, which is the number of protons in the nucleus of an atom of each element. This arrangement reflects the underlying structure of the elements and provides a systematic way to understand their properties and relationships.

The atomic number not only determines the identity of the element but also influences its chemical behavior, as it affects the electronic configuration of the atoms. As you move across the periodic table from left to right, elements usually exhibit trends in reactivity, electronegativity, and ionization energy due to the increasing number of protons and the accompanying increase in effective nuclear charge.

This organization of elements also leads to the formation of groups and periods, where elements in the same group (vertical columns) typically share similar chemical properties due to their comparable valence electron configurations. Therefore, the arrangement by increasing atomic number provides a coherent framework that reflects both the properties of the elements and their relationships to one another in the context of modern atomic theory.