Barrons SAT Subject Test Chemistry, 13th Edition

Summary of Quantum Numbers for the First Four Levels of Orbitals in the

Hydrogen Atom

Hund’s Rule of Maximum Multiplicity and the Aufbau Principle

It is important to remember that, when there is more than one orbital at a
particular energy level, such as three p orbitals or five d orbitals, only one
electron will fill each orbital until each has one electron. This principle, that an
electron occupies the lowest energy orbital that can receive it, is called the
Aufbau Principle. After this, pairing will occur with the addition of one more
electron to each orbital. This principle, called Hund’s Rule of Maximum
Multiplicity, is shown in Table 2, where each arrowhead indicates an electron (
).

TIP

Know the Aufbau Principle and Hund’s Rule of Maximum Multiplicity.

Table 2. Orbital Notations