When chlorine accepts an electron from sodium, it gains a negative charge. Here's why:

* Electrons have a negative charge.

* Chlorine starts neutral. It has the same number of protons (positive charge) and electrons (negative charge).

* By gaining an electron, chlorine now has one more negative charge than positive charge. This creates a net negative charge of -1.

So, after accepting the electron, chlorine becomes a chloride ion with a charge of -1.