Answer
Metal ion is Lewis acid. Ligand is Lewis base.
Work Step by Step
A Lewis acid is a substance that can accept a pair of electrons to form a new bond. They are sometimes referred to as electrophiles, or seekers of an additional electron pair. A Lewis base is a substance that can donate a pair of electrons to form a new bond. They are sometimes referred to as nucleophiles, or seekers of a positive nucleus. Metal ion (kation) accept a pair of electrons, so it is Lewis acid. Ligand is substance that gives pair of electrons, so it is Lewis base.
