Because sodium chloride contains sodium and chlorine elements, in the formation of compounds, the sodium element of the atom is easy to lose the outermost electron to meet the 8-electron stable structure, chlorine element of the atom is easy to get electrons to meet the 8-electron stable structure, then the sodium atom loses electrons to metal cations, chlorine atoms get electrons to anions, and then the use of anionic and cationic electrostatic effect to form compounds, that is, sodium chloride is composed of ionic composition, so the answer is: sodium ion and chloride ion (or Na + and Cl-).