Answer is: B. The third shell would be empty so that the eight electrons in the second level would be outermost after the atom loses one electron.
Neutral sodium atom has atomic number 11 (11 protons and 11 electrons).
Electron configuration of sodium atom: ₁₁Na 1s² 2s² 2p⁶ 3s¹.
Sodium lost one valence electron to form cation with stable electron configuration as noble gas neon (atomic number 10).
Electron configuration of sodium cation: ₁₁Na⁺ 1s² 2s² 2p⁶.