* Electronegativity: Electronegativity is a measure of an atom's ability to attract electrons in a chemical bond. Chlorine has a higher electronegativity (3.16) than sodium (0.93). This means chlorine has a stronger pull on shared electrons.

* Electron Configuration: Chlorine (Cl) has 7 valence electrons in its outer shell, making it one electron short of a full octet. This makes it highly reactive and eager to gain an electron to achieve stability. Sodium (Na) has only 1 valence electron, making it easier to lose that electron and achieve a stable configuration.

* Ionic Bonding: When sodium and chlorine react, sodium readily loses its valence electron, becoming a positively charged ion (Na+). Chlorine gains this electron, becoming a negatively charged ion (Cl-). This strong attraction between oppositely charged ions forms the ionic bond in sodium chloride (NaCl).

In essence, chlorine's higher electronegativity and its tendency to gain an electron make it much more attractive to electrons than sodium.