The number of electrons and protons is eleven in sodium. After sodium (Na) has transferred its electron to the chlorine atom (Cl) it becomes a positively charged ion. This is because as electrons are negatively charged, losing of an electron will increase the number of protons (i.e 11) as compared to the number of electrons (i.e 10) in sodium (Na) atom. Hence, a positive charge will be acquired by the sodium (Na) ions.
