* Sodium (Na) has a single electron in its outermost shell. It readily loses this electron to achieve a stable electron configuration like that of neon.

* Chlorine (Cl) has seven electrons in its outermost shell. It readily gains an electron to achieve a stable electron configuration like that of argon.

The reason sodium and chlorine readily combine is due to their opposite tendencies:

* Sodium wants to lose an electron (to become positively charged)

* Chlorine wants to gain an electron (to become negatively charged)

This difference in electronegativity (the tendency to attract electrons) creates an electrostatic attraction between the sodium and chloride ions, forming the ionic compound sodium chloride (NaCl), or table salt.