It is tempting to equate atoms and their corresponding ions but this would be a bad mistake. Neutral atoms and charged ions bear no resemblance in properties. The Chloride ion now has a total of eighteen electrons and seventeen protons for a net charge of minus one. The element Sodium is a soft metal, highly reactive in air and water. Hydrogen gas is produced with its' reaction in water.
Chlorine is a yellowish green gas with a strong bleach smell and is quite toxic.
Salt is . . . Again, the difference in neutral atoms and their respective ions is hard to overestimate. Notice a positively charged particle and a negatively charged particle were created in the reaction above. If these particles of opposite charge are close to each other, I'm sure you would predict the next step. Like charges repel and unlike attract so it is not surprising that these two ions attach for an Ionic Bond .