Final answer:
The elements in the periodic table are organized into sets called groups and periods. Elements in the same group have similar properties. Transition elements, or d-block elements, have unique electron configurations and their compounds often have bright colors.
Step-by-step explanation:
The elements in the periodic table are organized into sets based on their properties and electron arrangements. The periodic table is arranged in periods, which are horizontal rows, and groups, which are vertical columns. Elements within the same group have similar chemical properties. The transition elements, also known as the d-block elements, are located in the middle of the periodic table and have unique electron configurations. Transition element compounds often exhibit bright colors due to the arrangement of electrons in their outer shells.