Final answer:
The lightest element in Group 13 is the metalloid boron, which has the least mass among its group peers of aluminum, gallium, indium, and thallium. Aluminum is the lightest among the metals in Group 13.
Step-by-step explanation:
The student's question pertains to identifying the Group 13 metal with the least mass. Among the elements in Group 13, which include the metalloid boron and the metals aluminum, gallium, indium, and thallium, the one with the least mass is the metalloid boron. Boron is semiconducting, and unlike the metals in its group, its binary compounds tend to be covalent rather than ionic. The uniqueness of boron is underscored by its amphoteric oxides, exhibiting both nonmetallic and metallic behavior. The metallic members of Group 13 increase in mass as you move down the group, with aluminum being the lightest metal followed by gallium, indium, and thallium.