The bond formed between copper and fluorine is an ionic bond. This is because copper is a metal and fluorine is a non-metal. Metals and non-metals react to form ionic compounds, in which the metal atom loses electrons to the non-metal atom. This creates positively charged metal ions and negatively charged non-metal ions, which are attracted to each other by electrostatic forces. The ionic bond between copper and fluorine is formed by the transfer of one electron from the copper atom to the fluorine atom, resulting in a copper(I) ion (Cu+) and a fluoride ion (F-).