What is the primary purpose of electron configuration notation?

The primary purpose of electron configuration notation is to show the arrangement of electrons in an atom. This notation is crucial because it provides insight into how electrons are distributed among various energy levels and orbitals surrounding the nucleus. Understanding the arrangement of electrons is essential for predicting an atom’s chemical properties, including its bonding behavior and reactivity.

Electron configurations follow specific rules based on the principles of quantum mechanics, such as the Aufbau principle, Pauli exclusion principle, and Hund's rule. By indicating the number of electrons in each orbital and energy level (like 1s² 2s² 2p⁶), this notation helps chemists visualize how atoms interact with one another during chemical reactions. It lays the foundation for concepts like electron sharing in covalent bonds or the transfer of electrons in ionic bonds.

While the other options relate to aspects of atomic structure and behavior, they do not directly express the arrangement of electrons. Atomic mass pertains to the total number of protons and neutrons, chemical reactivity is influenced by electron arrangement but is a broader concept, and representing isotopes involves differences in neutron count rather than electron distribution. Thus, the electron configuration notation serves its primary purpose effectively by illustrating how electrons are structured around the nucleus of an atom.