when fomation of NaCl electron configuration Na loss one atom and Cl gain this atom in this situation Na and Cl are both atom are stable or not.
To determine which atom would lose an electron and which would accept one, we must focus on the amount of valence electrons on that atom (in other words, the amount of electrons in their outermost shell). Atoms like to attain the most stable energy level possible by having the maximum amount of electrons possible in its outermost shell but sometimes they can only do so through chemical reaction with other atoms. For the alkali metals, there is one electron in their outermost shell while halogens have seven. The full shell consists of eight electrons. As a result, it is much easier for halogens to obtain just one electron to complete the octet and for the alkali metal to lose that one remaining electron in its outermost shell so that their next outermost shell contains a full octet. This is what happens with Na and Cl. Na loses an electron to obtain a full octet while Cl obtains an electron to obtain a full octet. This creates Na+ and Cl-, which form an ionic interaction to become NaCl (neutral because + and - cancel each other out) commonly known as table salt.