What do we call the arrangement of electrons in an atom, described by principal energy level, sublevel, and number of electrons per sublevel?

The arrangement of electrons in an atom is termed electron configuration. This concept refers specifically to the distribution of electrons among the various energy levels and orbitals of an atom. In electron configuration, we specify the principal energy level, which indicates the distance of electrons from the nucleus, the sublevel (such as s, p, d, or f) that describes the shape of the orbital containing the electrons, and the number of electrons present in each sublevel.

Electron configuration provides a comprehensive way to depict how electrons are organized based on the principles of quantum mechanics. It is foundational for understanding the reactivity and properties of elements, as these configurations determine how atoms interact during chemical bonding.

In contrast, quantum number refers to the numerical values that describe the properties of atomic orbitals and the electrons in them but does not itself represent the arrangement in the full context of energy levels and electron distribution. Orbital notation visually represents the distribution of electrons but does not provide the same systematic account as electron configurations do. Energy level diagrams offer a graphical representation of the energy levels and sublevels but again lack the detailed account of electron distribution that the term electron configuration encapsulates.