Question

When there are two electrons in the same orbital, they have _______.

• A. same spins
• B. opposite spins
• C. different energies
• D. parallel spin

Answer 1

Answer: (B)

opposite spins

When there are two electrons in the same orbital, they have opposite spins. The Pauli exclusion principle states that there can only be a maximum of two electrons for every one orientation, and the two electrons must be opposite in spin direction; meaning one electron has $m_s=+\frac{1}{2}$ and the other electron has $m_s=-\frac{1}{2}$.