a) 1s² 2s² 2p⁶ 3s²
b) 1s² 2s² 2p⁶ 3s¹
c) 1s² 2s² 2p⁶ 3p¹
d) 1s² 2s² 2p⁶ 3s² 3p⁶
For Explanation Click Here:
Sodium (Na) has an atomic number of 11, so it has 11 electrons. The correct electron configuration is 1s² 2s² 2p⁶ 3s¹, with the last electron in the 3s orbital. This shows that sodium has one electron in its outermost shell, making it highly reactive.