Answer
According to the Pauli exclusion principle, no two electrons in atom can have the same set of four quantum numbers. In an orbital, the three quantum numbers (principle, orbital and magnetic) are the same, but there can be only two types of spin numbers +1/2 or -1/2. Hence, an orbital can have a maximum of two electrons with opposite spins as there is no third type of spin.
Work Step by Step
According to the Pauli exclusion principle, no two electrons in atom can have the same set of four quantum numbers. In an orbital, the three quantum numbers (principle, orbital and magnetic) are the same, but there can be only two types of spin numbers +1/2 or -1/2. Hence, an orbital can have a maximum of two electrons with opposite spins as there is no third type of spin.
