Here's why:
* Electron Configuration: Sodium has an electron configuration of 2, 8, 1. This means it has 2 electrons in its first shell, 8 in its second shell, and 1 in its third shell.
* Outer Shell: The third shell is the outer shell.
* Octet Rule: Atoms tend to be most stable when their outer shell has 8 electrons (except for hydrogen and helium which only need 2).
Therefore, sodium needs 7 more electrons to complete its outer shell and achieve a stable octet configuration.
