How is the periodic table organized?

The periodic table is organized by increasing atomic number, which is the number of protons in the nucleus of an atom of an element. This organization reflects the underlying structure of the elements, as the atomic number determines the element's identity and its position on the table. Each element is placed in order based on its atomic number, resulting in a systematic arrangement that also leads to an understanding of periodic trends in properties such as ionization energy, electronegativity, and atomic size.

While other methods like grouping elements by similar chemical properties can provide useful insights, they are secondary to the primary organization by atomic number. This arrangement inherently categorizes elements into periods (rows) and groups (columns) that exhibit related characteristics. For instance, elements in the same group typically have similar valence electron configurations and exhibit similar chemical behaviors.

Overall, the organization by increasing atomic number is fundamental to the periodic table's structure, serving as a guideline for predicting how elements will interact based on their position.