According to the Pauli exclusion principle, how many electrons can occupy an orbital?

The Pauli exclusion principle states that no two electrons in an atom can have the same set of four quantum numbers. Because of this principle, each orbital can accommodate a maximum of two electrons, but these electrons must have opposite spins to ensure they possess different quantum states. This is a fundamental concept in quantum mechanics and helps explain the arrangement of electrons within atoms.

When considering an orbital, such as an s, p, d, or f orbital, the characteristics of quantum numbers dictate that while the first electron can have a set of quantum values, the second must have a spin quantum number that is opposite to that of the first. Therefore, the correct interpretation of the Pauli exclusion principle directly leads to the conclusion that an orbital can hold a maximum of two electrons.