What does the number of shells tell you?

The number of shells in an atom corresponds to the number of energy levels or electron shells that surround the nucleus. Each shell can hold a specific number of electrons, and the arrangement of these electrons influences the atom's chemical properties and reactivity. Generally, elements with similar numbers of shells exhibit similar chemical behavior, as they belong to the same period in the Periodic Table. Additionally, the number of shells increases as you move down a group, indicating larger atomic size.