What is a defining feature of metalloids?

A defining feature of metalloids is that they possess properties of both metals and nonmetals. This dual characteristic allows metalloids to exhibit a range of behaviors and chemical properties that can resemble either category, depending on the elements with which they interact. For instance, metalloids can conduct electricity to some extent like metals, yet they may also form covalent bonds with nonmetals.

This property is particularly useful in applications such as semiconductors, where the ability to conduct electricity can be modulated by the presence of other substances. The unique position of metalloids in the periodic table, typically between metals and nonmetals, reflects their intermediate properties, making them crucial in various chemical and industrial contexts.

The other options do not accurately define metalloids. While it's true that many metalloids are solid at room temperature, this is not a defining feature because solid states can also apply to metals and nonmetals. The assertion that metalloids are located exclusively on the left side of the periodic table is incorrect; they are primarily found along a zig-zag line dividing metals and nonmetals. Lastly, stating that they are always gases is not true, as metalloids are predominantly solids at room temperature.