Chlorine and bromine are highly electronegative elements that typically do not lose electrons easily, making it challenging for them to form covalent compounds. Instead, they tend to share electrons, resulting in covalent bonds in various compounds like carbon tetrachloride (CCl4) and bromine monochloride (BrCl). While they can form covalent compounds, the energy required for them to lose electrons is significant, which influences their bonding behavior.