ANSWER
Option B
Step-by-step explanation
A sodium atom has equal number of protons and electrons. This is because a sodium atom is electrically stable
When a sodium atom participates in a chemical reaction, it automatically become a sodium ion because it wants to attain it octet structure.
When a sodium ion is formed then the one electron has been lost
Recall, that the number of protons of a sodium atom is 11.
Since the number of electrons is equal to the number of protons, then the number of electrons for a soidum atom is 11
For a sodium ion, the number of electron is 10 because it has lost an electron to attain it octet structure
Hence, the correct answer is 10 (Option B)