Sodium is much more apt to exist as a positive ion than is chlorine. Why does this occur?
Why? Well, this is the reason why educators teach electronic structure....
Metals are electron-rich materials....i.e. they are good reductants, and are LIKELY to lose electrons in their reaction chemistry....e.g.
On the other hand, elemental chlorine comes from the opposite side of the Periodic Table; these are electron-poor materials with HIGH nuclear charge. And so these non-metals are OXIDIZING, they tend to accept electrons....