The statement that the sodium atom loses an electron and the chlorine atom gains one is true in the formation of an ionic bond.
When sodium and chlorine react to form an ionic bond, the correct statement about the bonding that has occurred is A. The sodium atom has lost an electron and the chlorine atom has gained one. During this electron transfer, sodium (Na) donates its one valence electron to achieve a stable configuration, turning into a sodium cation (Na+) with an overall charge of +1. Chlorine (Cl), having seven electrons in its outer shell, accepts this electron, becoming a chloride anion (Cl−) with a net charge of -1. Both the sodium cation and chloride anion satisfy the octet rule, having complete outer electron shells, and because opposite charges attract, they form a strong ionic bond.