Answer : Option D) Copper and Fluorine atoms.
Explanation : An ionic bond is formed when a chemical bond is formed through an electrostatic force of attraction between two oppositely charged ions. These ionic bonds are formed between a cation, which is usually a metal, here, it is copper and an anion, which is usually a nonmetal is fluorine.
As ionic bonds are formed by transfer of electrons from the valence shell to another, these are strong bonds. The requirements of forming an ionic bond is fulfilled only by copper and fluorine in the given options.
Therefore, copper and fluorine atoms is the correct answer.
I think the correct answer from the choices listed above is option D. the substances cobalt and barium chloride will not react since cobalt os less active than barium so it does not have enough energy to displace barium in the compound. Hope this answers the question.
