Ions:
An [?] is an atom or group of atoms that has become electrically [?]. When an atom loses an [?], it loses a negative charge and becomes a positive [?]. When an atom gains an electron, it gains a [?] charge and becomes a negative [?].

Forming an Ionic Bond:
Follow what happens to sodium and chlorine atoms. The transfer of sodium's one valence [?] to chlorine changes both atoms into [?]. The sodium atom becomes a [?] ion (Na+) The chlorine atom becomes a [?] ion (Cl-). Negative and [?] electric charges attract each other, so the oppositely charged Na+ and Cl- [?] come together. They form sodium chloride, which you know as table salt.
An ionic [?] is the attraction between two oppositely charged [?]. This attraction is similar to the attraction between opposite poles of a magnet. When the two [?] come together, the opposite charges cancel out. Every sodium [?] (with a charge written as 1+) is balanced by a chloride [?] (with a charge written as 1-). The formula for sodium chloride, NaCl, shows you this 1:1 ratio.