Final answer:
A. representative elements. Elements in groups 1A through 8A of the periodic table are called representative elements, encompassing metals, nonmetals, and metalloids with last electrons filling the s or p orbitals.
Step-by-step explanation:
Elements in groups 1A through 8A of the periodic table are called representative elements. These elements, also known as main group elements, have their last electron added to the s or p orbitals in the highest energy level (outermost shell). The representative elements include a variety of metals, nonmetals, and metalloids, all of which exhibit typical properties of their respective categories, such as conductivity for metals and non-conductivity for nonmetals.
The other groups, specifically groups 3-12, consist of transition metals, characterized by the addition of electrons to the d orbitals.
Groups 1 and 2 of the representative elements consist of the alkali and alkaline earth metals, respectively. Groups 13 through 18 include other metals, nonmetals, and metalloids. Transition metals are found in groups 3 through 12 and display metallic properties, including high electrical and thermal conductivity. It's also important to note that groups 1A through 8A do not include the inner transition metals, which are the lanthanoids and actinides and occupy the separate block at the bottom of the periodic table.