How many positive ions of sodium are necessary to balance one ion of chlorine (chloride)?”
Sodium is a group I element and forms Na+ (excuse the lack of a superscript there) ions with a single electron missing from the outer shell. Chlorine is a halogen and gains a single electron, filling its outer shell, leaving Cl- ions. NaCl, then is a shorthand for the ionic solid containing equal numbers of sodium and chloride ions, with no overall charge: each chloride ion is balanced by a single Na+ ion.
