Is Matter Around Us Pure ? — Science STD 9 — Question

Along the border between nonmetals and metals are seven elements called metalloids. The metalloids have some characteristics of both metals and nonmetals. All are solids at room temperature. They are brittle, hard, and somewhat reactive. The most common metalloid is silicon (Si). The most useful property of the metalloids is their varying ability to conduct electricity. Whether or not a metalloid conducts electricity can depend on temperature, exposure to light, or the presence of small amounts os impurities. Semiconductors are substances that can conduct electricity under some conditions but not under other conditions.