Question

use the periodic table to answer the questions: which is the correct electron configuration for sodium (na)? 1s²2s²2p⁶2d¹ 1s²2s²2p⁶3s¹ 1s²2p⁶3d³

Explanation:

1. First, recall the atomic number of sodium (Na) is 11, so it has 11 electrons.
2. The electron - filling order follows the Aufbau principle: \(1s\), \(2s\), \(2p\), \(3s\), \(3p\), etc.

• The \(1s\) orbital can hold 2 electrons, \(2s\) can hold 2, \(2p\) can hold 6. After filling \(1s^{2}2s^{2}2p^{6}\), we have used \(2 + 2+6=10\) electrons.
• The remaining 1 electron goes into the \(3s\) orbital (not \(2d\) because the \(2d\) orbitals are not filled before \(3s\) in the Aufbau principle, and \(3d\) orbitals are filled much later).
• The first option has a \(2d^{1}\) which is incorrect as \(d\) orbitals in the \(n = 2\) shell are not filled at this stage. The third option has incorrect filling (missing \(2s\) and incorrect \(3d\) filling).

Answer:

B. \(1s^{2}2s^{2}2p^{6}3s^{1}\) (where B is the option corresponding to \(1s^{2}2s^{2}2p^{6}3s^{1}\))