Final answer:
The right side of the periodic table is less metallic because the elements there have a greater tendency to gain electrons and exhibit nonmetallic behavior, such as poor conductivity and a lack of luster, ductility, and malleability.
Step-by-step explanation:
The right side of the periodic table is less metallic when compared to the left side. This trend is due to periodic trends in metallic character. Specifically, as you move from left to right across a period, the atomic size decreases, which leads to valence electrons being more tightly held and thus more difficult to remove.
Metallic elements generally exhibit traits such as being good conductors of electricity, lustrous, ductile, and malleable, and they are predominantly found on the left side of the periodic table. Nonmetals, which are found on the right side, do not conduct electricity well (with the exception of graphite, a form of carbon), are not lustrous, ductile, or malleable, and tend to gain electrons during chemical reactions.