Final answer:
An element with a partially filled d sublevel in the ground state is classified as a transition metal, which is 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. The electron configuration of these elements features a d sublevel that is being filled with electrons, which is not fully occupied. In general, the higher s sublevel is either completely filled or has one electron missing before the d sublevel starts filling. For example, scandium (Sc) has an electron configuration of [Ar]3d¹ 4s².
Transition metals are found in Groups 3-12 of the periodic table, commonly referred to as the d-block elements. Notably, their compounds are often brightly colored due to transitions involving the d electrons. Moreover, transition elements such as chromium (Cr) and copper (Cu) may demonstrate exceptions where an electron from the 4s subshell is shifted into the 3d subshell to achieve a more stable electron configuration.