An ionic bond involves an ionic bond involves an attraction between ions of opposite charge water avoidance the sharing of a single pair of electrons the unequal sharing of an electron pair no atoms other than sodium and chlorine

In general chemistry, there are two types of bonding: ionic and covalent bonding. In ionic bonding, it is usually a bond between a metal and a nonmetal. For covalent bonds, these are usually both nonmetals. The main concept is that, electron in ionic bond are completely transferred. On the other hand, electrons in covalent bond are shared, either equally or unequally.

To achieve complete transfer of electrons, both elements must have a great difference in electronegativity. This is the property of the element to attract an electron towards itself. Hence, this is perfect between cations and anions. Cations are positively charged ions that have excess electrons. On the other hand, anions are negatively charged anions that lacks electrons in terms of stability. So, when these ions bond, they satisfy each other by giving one electron from the cation to the anion. 

So, the best answer is :an attraction between ions of opposite charges