Question 18
Apart from oxygen, which element is seen in the greatest quantity in the earth's crust?
The right answer is the one marked above.
Silicon — a metalloid.
Quartz and sand, and gems such as emerald, are crystalline silicon compounds; clay contains silicon too. Its melting point is 1410 °C, and it is used to make transistors, diodes, solar cells and computer components. Boron, the other metalloid you study, is used in welding metals, in skin ointments, and in glass that can be heated to high temperatures.