What does an electron shell represent in an atom?

An electron shell represents a grouping of electrons that are located at specific energy levels around the nucleus of an atom. Each shell can hold a certain number of electrons, and they are arranged according to their energy levels, with the closest shells to the nucleus having the lowest energy. As electrons occupy different shells, they enable the atom to participate in chemical bonding and reactions, influencing the atom's stability and reactivity.

Understanding the structure of electron shells is fundamental in chemistry and physics, as it explains how atoms interact with each other. The concept of electron shells also lays the groundwork for understanding other principles, such as electron configuration and the periodic table's organization.