Why are sodium and chlorine a good match for making a molecule?

Because sodium has the configuration of [Ne]3s1 it will empty the 3s orbital and create an ion with a charge of Na1+. Chlorine will do the opposite. Its configuration is [Ne]3s2,2p5 it will gain a electron to fill its s and p orbital. Because sodium doesnt want its extra s electron and chlorine is looking to gain a p electron, when the two react the electron is transferred to the chlorine. Their electronegativity is so far apart the it forms a stable Sodium Chloride molecule.