Regrettably, there is currently no Cu(OH)3 existent in nature or produced in laboratories. Chemistry does not acknowledge the existence of Cu(OH)3 because it conflicts with the ligand principle (the ultimate rule in Hund’s rules series). According to this principle, a Copper (Cu) atom can form a maximum of 4 chemical bonds.
Copper (II) hydroxide – Cu(OH)2 is sky-blue, capable of absorbing CO2 from the air. It can dissolve in ammoniac solution to form a dark-blue complex Cu(NH3)42.
Copper (I) hydroxide – CuOH is another version of copper hydroxide, but it is unstable, easily oxidized to Cu(OH)2. CuOH is black and insoluble in water.
Therefore, we cannot define Cu(OH)3 based on criteria such as nomenclature, atomic mass, molecular structure, ion structure, chemical and physical properties, as well as common chemical reactions and preparation methods in laboratories or industries.