* Sodium (Na) has a single electron in its outermost shell. It tends to lose this electron to achieve a stable, full outer shell, forming a positively charged sodium ion (Na+).

* Chlorine (Cl) has seven electrons in its outermost shell. It tends to gain one electron to achieve a stable, full outer shell, forming a negatively charged chloride ion (Cl-).

The combination of sodium and chlorine is driven by the opposite tendencies of the two atoms:

* Sodium wants to *lose* an electron.

* Chlorine wants to *gain* an electron.

The electrostatic attraction between the positively charged sodium ion and the negatively charged chloride ion is what forms the ionic bond in sodium chloride (NaCl), commonly known as table salt.