Which of the following elements is known to form compounds that are typically used in glassmaking?

Silicon is the primary element known for its significant role in glassmaking. The compounds formed from silicon, particularly silicon dioxide (SiO2), are the foundational materials in the production of glass. In glass, silicon dioxide provides the necessary structure and transparency, making it a critical component. The properties of silicon allow it to form a durable and stable network when combined with other materials, which is essential for the quality of glass used in various applications, from window panes to bottles.

While the other elements can be involved in certain types of glass formulations or contribute specific properties, none are as central to glassmaking as silicon. For instance, barium may be used in some specialty glasses for enhanced optical properties, aluminum can be included for strength in certain glass types, and iron can affect color, but it is silicon that forms the basic structure of glass itself. Thus, silicon is the clear choice for an element typically associated with glassmaking compounds.