Final answer:
An element with a partially filled D sublevel in the ground state is classified as a transition metal, found in Groups 3-12 on the periodic table.
Step-by-step explanation:
An element with a partially filled D sublevel in the ground state is classified as a transition metal. Transition metals are characterized by having incomplete d orbitals after the last noble gas configuration. These elements can be found in Groups 3-12 of the periodic table, which are often referred to as the d-block elements due to the involvement of the d orbital in their valence electron shell. Examples of transition metals include iron (Fe), copper (Cu), and gold (Au). They exhibit typical metallic properties and are generally less reactive than the metals found in Groups 1 and 2.