Which of these Elements is a metalloid?

The story behind the answer

Antimony (Sb) is a metalloid—elements that sit along the periodic table’s “staircase” and show properties between metals and nonmetals. It’s shiny and brittle like a metal but a poor conductor at room temperature like a nonmetal, and it can act as a semiconductor. In contrast, bromine is a halogen (nonmetal), tin is a post-transition metal, and rubidium is an alkali metal.

Remember it this way: “Sb” comes from stibium, historically used as kohl; think “Sb = semi-both,” hinting at its semi-metal nature. Antimony is used in flame retardants, hardening alloys (like battery grids), and as a dopant in semiconductors.