Final answer:
Boron is the lightest semi-metal on the periodic table, found in Group 13, and exhibits properties between those of metals and nonmetals.
Step-by-step explanation:
The lightest semi-metal on the periodic table is boron. Within Group 13 of the periodic table, boron is classified as a metalloid, or semi-metal, due to its properties that are intermediate between metals and nonmetals. Boron is semiconducting, and its binary compounds are primarily covalent rather than ionic. Comparatively, the remaining elements in Group 13, such as aluminum, gallium, indium, and thallium, are considered metals, with indium and thallium exhibiting clearly metallic character. Another interesting fact about this group is that gallium has a melting point of about 30 °C and can melt in your hand.