Final answer:
The correct formula of the compound formed when sodium and chlorine react is NaCl.
Step-by-step explanation:
When sodium (Na) and chlorine (Cl) react, the sodium atom loses one electron to form a Na+ ion with a stable noble gas configuration of [Ne]. The chlorine atom gains one electron to form a Cl- ion with a stable noble gas configuration of [Ne]3s23p6.
In the compound formed, the Na+ ion and the Cl- ion combine in a 1:1 ratio to form NaCl. So the correct formula of the compound when sodium and chlorine react is NaCl.