Final answer:
Silicon is the second most abundant element in the Earth's crust and is used in various applications.
Step-by-step explanation:
The second most abundant element in the Earth's crust is silicon. It makes up nearly one-fourth of the mass of the crust, second only to oxygen. Silicon is the principal component of sand and quartz and finds use in various applications such as solar cells, computer chips, caulking materials, and abrasives.