Here's why:
* Sodium (Na): Sodium has one valence electron. By losing this electron, it becomes a positively charged ion (Na+) with a full outer shell of 2 electrons, achieving the electron configuration of neon (Ne).
* Chlorine (Cl): Chlorine has seven valence electrons. By gaining one electron, it becomes a negatively charged ion (Cl-) with a full outer shell of 8 electrons, achieving the electron configuration of argon (Ar).
This is a common trend in ionic bonding – atoms tend to gain or lose electrons to achieve the stable electron configuration of the nearest noble gas. This stability is due to the filled outer electron shells of noble gases, making them relatively unreactive.
