Here's how to determine the electron configuration of a sodium ion (Na+):

1. Start with the neutral atom:

* Sodium (Na) has an atomic number of 11, meaning it has 11 protons and 11 electrons.

* Its electron configuration is: 1s² 2s² 2p⁶ 3s¹

2. Ionization:

* Sodium loses one electron to become a positively charged ion (Na+).

* This electron is lost from the outermost shell (3s¹).

3. Final electron configuration:

* The electron configuration of Na+ is: 1s² 2s² 2p⁶

Therefore, the correct electron configuration for a sodium ion is 1s² 2s² 2p⁶.