What sublevel is the one filling across the transition elements?

The main transition elements, or metals, are located in the middle of the periodic table starting in Group IIA and extending to Group IIB. These elements are also known as the d-block elements, because their d orbitals are the highest energy level orbitals that are filled or partially filled.

The transition elements are known as transition metals because they have similar properties to the metallic elements on the periodic table, according to Georgia State University. All the transition elements also share properties with each other. Some of these properties, which are dependent on their filled and partially filled d-orbitals, include having high melting points and numerous oxidation states.