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List all allowed quantum numbers for n = 2 and count the orbitals. Step 1: n = 2 → l = 0, 1. Step 2: l = 0 (2s): m_l = 0 → 1 orbital. Step 3: l = 1 (2p): m_l = −1, 0, +1 → 3 orbitals. Step 4: Total orbitals = 4; with spin, max 8 electrons. General rule: n² orbitals, 2n² electrons per shell.