Final answer:
Highly electronegative atoms tend to form anions, which are negatively charged ions resulting from the gain of electrons. These anions are formed due to the atoms' strong electron affinity and high ionization energy, both conducive to gaining electrons and not losing them.
Step-by-step explanation:
Highly electronegative atoms tend to form anions because they have a large (negative) electron affinity and a high ionization energy. These atoms attract electrons from other elements during bond formation to achieve a more stable electronic configuration, which resembles the nearest noble gas. When a highly electronegative atom gains electrons, it becomes negatively charged, thus forming an anion. For example, chlorine will gain an electron to form a chloride anion.
In the context of an ionic bond, when a highly electronegative atom forms a bond with a less electronegative atom, the difference in electronegativity between the two leads to the transfer of electrons. This transfer results in the formation of ions: the atom losing electrons becomes a cation (positively charged), and the electronegative atom that gains electrons becomes an anion (negatively charged). The ions are then held together by the electrostatic forces of attraction between the oppositely charged particles.