Answer:
It looses an electron
Step-by-step explanation:
We must remember that sodium chloride is an ionic compound. In an ionic compound, a metal is often bonded to a non metal.
The metal looses electron(s) and the nonmetal accepts electron(s). The metal forms its cation while the non metal forms its anion.
Thus an ionic compound is basically a pair of ions held by electrostatic interaction.
Thus, when chlorine becomes part of sodium chloride, it gains one electron from sodium and becomes Cl^-