Question

which of the following is a reasonable electron configuration? 1s²2s²2p⁶3s² 1s²2s²2p⁶3s²3d⁴ 1s²2s²2d¹⁰2p³ 1s²2s²2p³2d⁶

Explanation:

Step1: Recall electron - filling rules

Electrons fill orbitals in the order of increasing energy following the Aufbau principle. The order of filling is \(1s<2s < 2p<3s<3p < 4s<3d<4p\cdots\). Also, the \(s\) - subshell can hold a maximum of 2 electrons, the \(p\) - subshell can hold a maximum of 6 electrons, and the \(d\) - subshell can hold a maximum of 10 electrons.

Step2: Analyze each option

• Option 1: \(1s^{2}2s^{2}2p^{6}3s^{2}\) follows the Aufbau principle. The \(1s\) sub - shell is filled with 2 electrons, the \(2s\) sub - shell is filled with 2 electrons, the \(2p\) sub - shell is filled with 6 electrons, and then the \(3s\) sub - shell is filled with 2 electrons.
• Option 2: In \(1s^{2}2s^{2}2p^{6}3s^{2}3d^{4}\), according to the Aufbau principle, after filling \(3s^{2}\), the next sub - shell to be filled is \(3p\) before \(3d\). So this is incorrect.
• Option 3: There is no \(2d\) sub - shell. The first \(d\) sub - shell appears in the \(n = 3\) energy level. So \(1s^{2}2s^{2}2d^{10}2p^{3}\) is incorrect.
• Option 4: There is no \(2d\) sub - shell. So \(1s^{2}2s^{2}2p^{3}2d^{6}\) is incorrect.

Answer:

\(1s^{2}2s^{2}2p^{6}3s^{2}\)