Final answer:
The rectangle between halogens and transition metals on the periodic table is known as the transition metals (Group 3-12).
Step-by-step explanation:
The rectangle between the halogens and the transition metals on a periodic table is known as Group 3-12, which includes the transition metals. This classification is due to these elements' ability to transition between different oxidation states, unlike the highly reactive alkali metals in Group 1 or the alkaline earth metals in Group 2. Transition metals are characterized by their malleability, ductility, and electrical conductivity.
On the opposite side of the periodic table from transition metals, Group 17 hosts the halogens, which are highly reactive nonmetals that readily form salts with metals. Directly to the right of halogens, Group 18 consists of the noble gases, which are inert and the least reactive elements.
Therefore, the answer to the question is D) Transition metals.