Final answer:
Chlorine has a higher electron affinity and more electron shells than sodium, making it more likely to gain electrons. Sodium, with its lower ionization energy, readily loses its outer electron, becoming a cation, while chlorine gains this electron, turning into an anion; both satisfy the octet rule.
Step-by-step explanation:
Sodium is more likely to form a cation than chlorine because chlorine has a higher electron affinity and a higher number of electron shells. This higher electron affinity means chlorine is more inclined to gain electrons rather than lose them. When sodium (which has a low ionization energy), with its single electron in the outer shell, comes into contact with chlorine, which has seven electrons in its outer shell, electron transfer occurs. The sodium atom loses one electron, resulting in a sodium cation (Na+) with a +1 charge, fulfilling the octet rule by having complete outer shells.
Conversely, the chlorine atom gains an electron to become a chloride anion (Cl−) with a -1 charge. This process not only satisfies the octet rule for chlorine by filling its outer shell but also creates a strong ionic bond between the oppositely charged ions, leading to the formation of the ionic compound sodium chloride (NaCl), commonly known as table salt. The reaction between Na and Cl to form Na+ and Cl− ions constitutes an essential behavior in ionic bonding and the creation of stable ionic compounds.