Final answer:
When a very electronegative atom strips a valence electron away from its partner, ions form and this forms an ionic bond.
Step-by-step explanation:
When a very electronegative atom strips a valence electron away from its partner, ions form. This is because the atom that loses the electron becomes positively charged (cation) while the atom that gains the electron becomes negatively charged (anion). This strong electrostatic attraction between oppositely charged ions forms an ionic bond.