When sodium reacts with chlorine, the sodium atom transfers 1 electron to the chlorine atom, in order to achieve a stable electron configuration resembling a noble gas. The sodium (Na) atom becomes a sodium Na+ ion, and the chlorine (Cl) atom becomes a chloride Cl- ion. Strong electrostatic forces of attraction between the two ions cause them to form the ionic compound sodium chloride (NaCl).(In this question, dot-cross diagrams could be used to better demonstrate the candidates understanding of the electron transfer)