Silicate minerals form from cooling of molten rock and are built from which two elements bonded into tetrahedra?

• A. Silica and Oxygen
• B. Sodium and Chlorine
• C. Calcium and Carbonate
• D. Aluminum and Fluorine

Answer: (A)

The key idea is that silicate minerals are built from silicon-oxygen tetrahedra. In each tetrahedron, a silicon atom sits at the center and bonds to four oxygen atoms at the corners, forming SiO4. As magma cools and minerals crystallize, these SiO4 units share oxygen atoms with each other to build the many structures seen in silicates, from isolated tetrahedra to chains, sheets, and three-dimensional frameworks. So the essential elements in this basic building block are silicon and oxygen.

Other elements mentioned (like sodium, chlorine, calcium, aluminum, fluorine) can be present in silicate minerals, but they don’t form the fundamental tetrahedral unit themselves. They may substitute for other cations or occupy spaces in the crystal structure, but the SiO4 tetrahedron, the silicon-oxygen unit, is the core building block of silicate minerals.