Final answer:
Sodium and chlorine react readily because sodium donates an electron to chlorine, forming a stable ionic bond and resulting in the formation of sodium chloride or table salt.
Step-by-step explanation:
The reaction between sodium (Na) and chlorine (Cl) to form sodium chloride (NaCl) occurs readily due to the transfer of electrons from sodium to chlorine, forming an ionic bond. Sodium, being a very reactive metal, has a single electron in its outermost shell that it readily donates. Chlorine, on the other hand, is a highly electronegative gas that needs one more electron to complete its outer shell. When these two elements come into contact, sodium transfers its extra electron to chlorine, resulting in the formation of Na+ and Cl- ions. This exchange is highly exothermic, releasing a great amount of light and heat. Consequently, the two elements form a stable ionic compound known as sodium chloride, or table salt, which is necessary for various bodily functions and is a part of our daily diet.