Metallic elements tend to act as lewis acids and form complexes with a variety of lewis bases. since most elements are metals, and almost all metals form complexes, it is important to understand these complexes. many biological molecules, such as the chlorophyll used by plants to harvest the energy of sunlight, are coordination compounds or compounds containing one or more metal complexes. part a arrange the complexes in order of decreasing stability. rank from most stable to least stable. to rank items as equivalent, overlap them. [cu(nh3)6]2+ [cuf6]2+ [cu(en)3]2+ [cu(en)(h2o)4]2+