Final answer:
The correct chemical formula for copper chloride depends on the oxidation state of copper, which forms multiple ions, resulting in compounds with different copper-to-chlorine ratios and thus different chemical formulas, CuCl for copper(I) and CuCl2 for copper(II).
Step-by-step explanation:
The reason it is not possible to write a correct chemical formula for copper chloride without more information is that copper can form more than one type of ion, resulting in different compounds. Specifically, copper can form a Cu+ ion, leading to the compound copper(I) chloride with the formula CuCl, or it can form a Cu2+ ion, leading to the compound copper(II) chloride with the formula CuCl2. The correct formula of a copper chloride compound depends on the oxidation state of the copper ion. Additionally, ionic compounds do not exist as molecules but instead form a crystal lattice structure with a fixed ratio of ions. This is why we need the correct ratio of ions to write an empirical formula that represents the ionic compound accurately.
An empirical formula, such as NaCl for sodium chloride, only indicates the ratio of ions in the compound, not the actual layout of atoms in the solid structure. Similarly, for copper chloride, we need to know whether it is copper(I) or copper(II) chloride to state the correct empirical formula. In the first case, with a copper-to-chlorine ratio of 1:1, the chemical formula is CuCl. In the second, with a 1:2 ratio, it is CuCl2. Transition metal compounds, like those containing copper, often have complex structures and the empirical formula does not reflect these complexities.